101 LINQ Samples in Dart
Port of the C# 101 LINQ Samples rewritten into idiomatic Dart and utilizing its functional collection mixins.
Compare Dart to other LINQ examples written in:
Call .NET Web Services from Dart
If you're looking for an effortles typed API for consuming .NET Web Services in Flutter, Dart VM, AngularDart or Dart Web Apps checkout ServiceStack's Dart Add ServiceStack Reference.
Running the examples
You can choose to run specific examples by commenting the sections you're not interested in play.dart.
To see the full output of all the examples, run play.dart locally.
Contents
The samples below mirrors the C# LINQ samples layout with the names of the top-level Dart methods matching their corresponding C# examples.
LINQ - Restriction Operators / MSDN C#
LINQ - Projection Operators / MSDN C#
LINQ - Partitioning Operators / MSDN C#
LINQ - Ordering Operators / MSDN C#
LINQ - Grouping Operators / MSDN C#
LINQ - Set Operators / MSDN C#
LINQ - Conversion Operators / MSDN C#
LINQ - Element Operators / MSDN C#
LINQ - Generation Operators / MSDN C#
LINQ - Quantifiers / MSDN C#
LINQ - Aggregate Operators / MSDN C#
LINQ - Miscellaneous Operators / MSDN C#
LINQ - Query Execution / MSDN C#
LINQ - Join Operators / MSDN C#
Side-by-side - C# LINQ vs Dart functional collections
For a side-by-side comparison, the original C# source code is displayed above the equivalent Dart translation.
- The Output shows the console output of running the Dart sample.
- Outputs ending with
...illustrates only a partial response is displayed. - The source-code for C# and Dart utils used are included once under the first section they're used in.
- The C# ObjectDumper util used is downloadable from MSDN - ObjectDumper.zip
LINQ - Restriction Operators
linq1: Where - Simple 1
//c#
public void Linq1()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var lowNums =
from n in numbers
where n < 5
select n;
Console.WriteLine("Numbers < 5:");
foreach (var x in lowNums)
{
Console.WriteLine(x);
}
} //dart
linq1(){
var numbers = [5, 4, 1, 3, 9, 8, 6, 7, 2, 0];
var lowNums = numbers
.where((n) => n < 5);
print("Numbers < 5:");
lowNums.forEach(print);
}Output
Numbers < 5:
4
1
3
2
0
linq2: Where - Simple 2
//c#
public void Linq2()
{
List<Product> products = GetProductList();
var soldOutProducts =
from p in products
where p.UnitsInStock == 0
select p;
Console.WriteLine("Sold out products:");
foreach (var product in soldOutProducts)
{
Console.WriteLine("{0} is sold out!", product.ProductName);
}
} //dart
linq2(){
var products = productsList();
var soldOutProducts = products
.where((p) => p.unitsInStock == 0);
print("Sold out products:");
soldOutProducts.forEach((p) => print("${p.productName} is sold out!"));
}Output
Sold out products:
Chef Anton's Gumbo Mix is sold out!
Alice Mutton is sold out!
Th�ringer Rostbratwurst is sold out!
Gorgonzola Telino is sold out!
Perth Pasties is sold out!
linq3: Where - Simple 3
//c#
public void Linq3()
{
List<Product> products = GetProductList();
var expensiveInStockProducts =
from p in products
where p.UnitsInStock > 0 && p.UnitPrice > 3.00M
select p;
Console.WriteLine("In-stock products that cost more than 3.00:");
foreach (var product in expensiveInStockProducts)
{
Console.WriteLine("{0} is in stock and costs more than 3.00.", product.ProductName);
}
} //dart
linq3(){
var products = productsList();
var expensiveInStockProducts = products
.where((p) => p.unitsInStock > 0 && p.unitPrice > 3.00);
print("In-stock products that cost more than 3.00:");
expensiveInStockProducts.forEach((p) =>
print("${p.productName} is in stock and costs more than 3.00."));
} Output
In-stock products that cost more than 3.00:
Chai is in stock and costs more than 3.00.
Chang is in stock and costs more than 3.00.
Aniseed Syrup is in stock and costs more than 3.00.
...
linq4: Where - Drilldown
//c#
public void Linq4()
{
List<Customer> customers = GetCustomerList();
var waCustomers =
from c in customers
where c.Region == "WA"
select c;
Console.WriteLine("Customers from Washington and their orders:");
foreach (var customer in waCustomers)
{
Console.WriteLine("Customer {0}: {1}", customer.CustomerID, customer.CompanyName);
foreach (var order in customer.Orders)
{
Console.WriteLine(" Order {0}: {1}", order.OrderID, order.OrderDate);
}
}
} //dart
linq4(){
var customers = customersList();
var waCustomers = customers
.where((c) => c.region == "WA");
print("Customers from Washington and their orders:");
waCustomers.forEach((Customer c){
print("Customer ${c.customerId}: ${c.companyName}");
c.orders.forEach((o) => print(" Order ${o.orderId}: ${o.orderDate}"));
});
}Output
Customers from Washington and their orders:
Customer LAZYK: Lazy K Kountry Store
Order 10482: 1997-03-21T00:00:00
Order 10545: 1997-05-22T00:00:00
Customer TRAIH: Trail's Head Gourmet Provisioners
Order 10574: 1997-06-19T00:00:00
Order 10577: 1997-06-23T00:00:00
Order 10822: 1998-01-08T00:00:00
...
linq5: Where - Indexed
//c#
public void Linq5()
{
string[] digits = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
var shortDigits = digits.Where((digit, index) => digit.Length < index);
Console.WriteLine("Short digits:");
foreach (var d in shortDigits)
{
Console.WriteLine("The word {0} is shorter than its value.", d);
}
}//dart
linq5(){
var digits = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"];
int index=0;
var shortDigits = digits.where((digit) => digit.length < index++);
print("Short digits:");
shortDigits.forEach((d) => print("The word $d is shorter than its value."));
}Output
Short digits:
The word five is shorter than its value.
The word six is shorter than its value.
The word seven is shorter than its value.
The word eight is shorter than its value.
The word nine is shorter than its value.
LINQ - Projection Operators
linq6: Select - Simple 1
//c#
public void Linq6()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var numsPlusOne =
from n in numbers
select n + 1;
Console.WriteLine("Numbers + 1:");
foreach (var i in numsPlusOne)
{
Console.WriteLine(i);
}
}//dart
linq6(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var numsPlusOne = numbers
.map((n) => n + 1);
print("Numbers + 1:");
numsPlusOne.forEach(print);
}Output
Numbers + 1:
6
5
2
4
10
9
7
8
3
1
linq7: Select - Simple 2
//c#
public void Linq7()
{
List<Product> products = GetProductList();
var productNames =
from p in products
select p.ProductName;
Console.WriteLine("Product Names:");
foreach (var productName in productNames)
{
Console.WriteLine(productName);
}
}//dart
linq7(){
var products = productsList();
var productNames = products
.map((p) => p.productName);
print("Product Names:");
productNames.forEach(print);
}Output
Product Names:
Chai
Chang
Aniseed Syrup
Chef Anton's Cajun Seasoning
Chef Anton's Gumbo Mix
...
linq8: Select - Transformation
//c#
public void Linq8()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
var textNums =
from n in numbers
select strings[n];
Console.WriteLine("Number strings:");
foreach (var s in textNums)
{
Console.WriteLine(s);
}
}//dart
linq8(){
var numbers = [5, 4, 1, 3, 9, 8, 6, 7, 2, 0];
var strings = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"];
var textNums = numbers
.map((n) => strings[n]);
print("Number strings:");
textNums.forEach(print);
}Output
Number strings:
five
four
one
three
nine
eight
six
seven
two
zero
linq9: Select - Anonymous Types 1
//c#
public void Linq9()
{
string[] words = { "aPPLE", "BlUeBeRrY", "cHeRry" };
var upperLowerWords =
from w in words
select new { Upper = w.ToUpper(), Lower = w.ToLower() };
foreach (var ul in upperLowerWords)
{
Console.WriteLine("Uppercase: {0}, Lowercase: {1}", ul.Upper, ul.Lower);
}
}//dart
linq9(){
var words = ["aPPLE", "BlUeBeRrY", "cHeRry"];
var upperLowerWords = words
.map((w) => { 'Upper': w.toUpperCase(), 'Lower': w.toLowerCase() });
upperLowerWords.forEach((ul) =>
print("Uppercase: ${ul['Upper']}, Lowercase: ${ul['Lower']}"));
}Output
Uppercase: APPLE, Lowercase: apple
Uppercase: BLUEBERRY, Lowercase: blueberry
Uppercase: CHERRY, Lowercase: cherry
linq10: Select - Anonymous Types 2
//c#
public void Linq10()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
var digitOddEvens =
from n in numbers
select new { Digit = strings[n], Even = (n % 2 == 0) };
foreach (var d in digitOddEvens)
{
Console.WriteLine("The digit {0} is {1}.", d.Digit, d.Even ? "even" : "odd");
}
}//dart
linq10(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var strings = [ "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" ];
var digitOddEvens = numbers
.map((n) => { 'Digit': strings[n], 'Even': (n % 2 == 0) });
digitOddEvens.forEach((d) =>
print("The digit ${d['Digit']} is ${d['Even'] ? 'even' : 'odd'}."));
}Output
The digit five is odd.
The digit four is even.
The digit one is odd.
The digit three is odd.
The digit nine is odd.
The digit eight is even.
The digit six is even.
The digit seven is odd.
The digit two is even.
The digit zero is even.
linq11: Select - Anonymous Types 3
//c#
public void Linq11()
{
List<Product> products = GetProductList();
var productInfos =
from p in products
select new { p.ProductName, p.Category, Price = p.UnitPrice };
Console.WriteLine("Product Info:");
foreach (var productInfo in productInfos)
{
Console.WriteLine("{0} is in the category {1} and costs {2} per unit.", productInfo.ProductName, productInfo.Category, productInfo.Price);
}
}//dart
linq11(){
var products = productsList();
var productInfos = products
.map((p) => { 'ProductName':p.productName, 'Category':p.category, 'Price': p.unitPrice });
print("Product Info:");
productInfos.forEach((p) =>
print("${p['ProductName']} is in the category ${p['Category']} and costs ${p['Price']} per unit."));
}Output
Product Info:
Chai is in the category Beverages and costs 18.0 per unit.
Chang is in the category Beverages and costs 19.0 per unit.
Aniseed Syrup is in the category Condiments and costs 10.0 per unit.
...
linq12: Select - Indexed
//c#
public void Linq12()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var numsInPlace = numbers.Select((num, index) => new { Num = num, InPlace = (num == index) });
Console.WriteLine("Number: In-place?");
foreach (var n in numsInPlace)
{
Console.WriteLine("{0}: {1}", n.Num, n.InPlace);
}
}//dart
linq12(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
int index = 0;
var numsInPlace = numbers
.map((num) => { 'Num': num, 'InPlace': (num == index++) });
print("Number: In-place?");
numsInPlace.forEach((n) =>
print("${n['Num']}: ${n['InPlace']}"));
}Output
Number: In-place?
5: false
4: false
1: false
3: true
9: false
8: false
6: true
7: true
2: false
0: false
linq13: Select - Filtered
//c#
public void Linq13()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
string[] digits = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
var lowNums =
from n in numbers
where n < 5
select digits[n];
Console.WriteLine("Numbers < 5:");
foreach (var num in lowNums)
{
Console.WriteLine(num);
}
}//dart
linq13(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var digits = [ "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" ];
var lowNums = numbers
.where((n) => n < 5)
.map((n) => digits[n]);
print("Numbers < 5:");
lowNums.forEach(print);
}Output
Numbers < 5:
four
one
three
two
zero
linq14: SelectMany - Compound from 1
//c#
public void Linq14()
{
int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
int[] numbersB = { 1, 3, 5, 7, 8 };
var pairs =
from a in numbersA
from b in numbersB
where a < b
select new { a, b };
Console.WriteLine("Pairs where a < b:");
foreach (var pair in pairs)
{
Console.WriteLine("{0} is less than {1}", pair.a, pair.b);
}
}//dart
linq14(){
var numbersA = [ 0, 2, 4, 5, 6, 8, 9 ];
var numbersB = [ 1, 3, 5, 7, 8 ];
var pairs = numbersA
.expand((a) => numbersB
.where((b) => a < b)
.map((b) => { 'a':a, 'b':b }));
print("Pairs where a < b:");
pairs.forEach((pair) =>
print("${pair['a']} is less than ${pair['b']}"));
}Output
Pairs where a < b:
0 is less than 1
0 is less than 3
0 is less than 5
0 is less than 7
0 is less than 8
2 is less than 3
2 is less than 5
2 is less than 7
2 is less than 8
4 is less than 5
4 is less than 7
4 is less than 8
5 is less than 7
5 is less than 8
6 is less than 7
6 is less than 8
linq15: SelectMany - Compound from 2
//c#
public void Linq15()
{
List<Customer> customers = GetCustomerList();
var orders =
from c in customers
from o in c.Orders
where o.Total < 500.00M
select new { c.CustomerID, o.OrderID, o.Total };
ObjectDumper.Write(orders);
}//dart
linq15(){
var customers = customersList();
var orders = customers
.expand((c) => c.orders
.where((o) => o.total < 500)
.map((o) => { 'CustomerId': c.customerId, 'OrderId':o.orderId, 'Total':o.total }));
orders.forEach(print);
}Output
{CustomerId: ALFKI, OrderId: 10702, Total: 330.0}
{CustomerId: ALFKI, OrderId: 10952, Total: 471.2}
{CustomerId: ANATR, OrderId: 10308, Total: 88.8}
{CustomerId: ANATR, OrderId: 10625, Total: 479.75}
...
linq16: SelectMany - Compound from 3
//c#
public void Linq16()
{
List<Customer> customers = GetCustomerList();
var orders =
from c in customers
from o in c.Orders
where o.OrderDate >= new DateTime(1998, 1, 1)
select new { c.CustomerID, o.OrderID, o.OrderDate };
ObjectDumper.Write(orders);
}//dart
linq16(){
var customers = customersList();
var orders = customers
.expand((c) => c.orders
.where((o) => o.orderDate.isAfter(new DateTime(1998, 1, 1)))
.map((o) => { 'CustomerId': c.customerId, 'OrderId':o.orderId, 'OrderDate':o.orderDate }));
orders.forEach(print);
}Output
{CustomerId: ALFKI, OrderId: 10835, OrderDate: 1998-01-15 00:00:00.000}
{CustomerId: ALFKI, OrderId: 10952, OrderDate: 1998-03-16 00:00:00.000}
{CustomerId: ALFKI, OrderId: 11011, OrderDate: 1998-04-09 00:00:00.000}
{CustomerId: ANATR, OrderId: 10926, OrderDate: 1998-03-04 00:00:00.000}
{CustomerId: ANTON, OrderId: 10856, OrderDate: 1998-01-28 00:00:00.000}
...
linq17: SelectMany - from Assignment
//c#
public void Linq17()
{
List<Customer> customers = GetCustomerList();
var orders =
from c in customers
from o in c.Orders
where o.Total >= 2000.0M
select new { c.CustomerID, o.OrderID, o.Total };
ObjectDumper.Write(orders);
}//dart
linq17(){
var customers = customersList();
var orders = customers
.expand((c) => c.orders
.where((o) => o.total >= 2000)
.map((o) => { 'CustomerId': c.customerId, 'OrderId':o.orderId, 'Total':o.total }));
orders.forEach(print);
}Output
{CustomerId: ANTON, OrderId: 10573, Total: 2082.0}
{CustomerId: AROUT, OrderId: 10558, Total: 2142.9}
{CustomerId: AROUT, OrderId: 10953, Total: 4441.25}
{CustomerId: BERGS, OrderId: 10384, Total: 2222.4}
{CustomerId: BERGS, OrderId: 10524, Total: 3192.65}
...
linq18: SelectMany - Multiple from
//c#
public void Linq18()
{
List<Customer> customers = GetCustomerList();
DateTime cutoffDate = new DateTime(1997, 1, 1);
var orders =
from c in customers
where c.Region == "WA"
from o in c.Orders
where o.OrderDate >= cutoffDate
select new { c.CustomerID, o.OrderID };
ObjectDumper.Write(orders);
}//dart
linq18(){
var customers = customersList();
var cutoffDate = new DateTime(1997, 1, 1);
var orders = customers
.where((c) => c.region == "WA")
.expand((c) => c.orders
.where((o) => o.orderDate.isAfter(cutoffDate))
.map((o) => { 'CustomerId': c.customerId, 'OrderId':o.orderId }));
orders.forEach(print);
}Output
{CustomerId: LAZYK, OrderId: 10482}
{CustomerId: LAZYK, OrderId: 10545}
{CustomerId: TRAIH, OrderId: 10574}
{CustomerId: TRAIH, OrderId: 10577}
{CustomerId: TRAIH, OrderId: 10822}
{CustomerId: WHITC, OrderId: 10469}
{CustomerId: WHITC, OrderId: 10483}
{CustomerId: WHITC, OrderId: 10504}
{CustomerId: WHITC, OrderId: 10596}
{CustomerId: WHITC, OrderId: 10693}
{CustomerId: WHITC, OrderId: 10696}
{CustomerId: WHITC, OrderId: 10723}
{CustomerId: WHITC, OrderId: 10740}
{CustomerId: WHITC, OrderId: 10861}
{CustomerId: WHITC, OrderId: 10904}
{CustomerId: WHITC, OrderId: 11032}
{CustomerId: WHITC, OrderId: 11066}
linq19: SelectMany - Indexed
//c#
public void Linq19()
{
List<Customer> customers = GetCustomerList();
var customerOrders =
customers.SelectMany(
(cust, custIndex) =>
cust.Orders.Select(o => "Customer #" + (custIndex + 1) +
" has an order with OrderID " + o.OrderID));
ObjectDumper.Write(customerOrders);
}//dart
linq19(){
var customers = customersList();
int custIndex = 0;
var customerOrders =
customers.expand((cust){
custIndex++;
return cust.orders.map((o) =>
"Customer #${custIndex} has an order with OrderID ${o.orderId}");
});
customerOrders.forEach(print);
}Output
Customer #1 has an order with OrderID 10643
Customer #1 has an order with OrderID 10692
Customer #1 has an order with OrderID 10702
Customer #1 has an order with OrderID 10835
Customer #1 has an order with OrderID 10952
Customer #1 has an order with OrderID 11011
Customer #2 has an order with OrderID 10308
Customer #2 has an order with OrderID 10625
Customer #2 has an order with OrderID 10759
Customer #2 has an order with OrderID 10926
...
LINQ - Partitioning Operators
linq20: Take - Simple
//c#
public void Linq20()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var first3Numbers = numbers.Take(3);
Console.WriteLine("First 3 numbers:");
foreach (var n in first3Numbers)
{
Console.WriteLine(n);
}
}//dart
linq20(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var first3Numbers = numbers.take(3);
print("First 3 numbers:");
first3Numbers.forEach(print);
}Output
First 3 numbers:
5
4
1
linq21: Take - Nested
//c#
public void Linq21()
{
List<Customer> customers = GetCustomerList();
var first3WAOrders = (
from c in customers
from o in c.Orders
where c.Region == "WA"
select new { c.CustomerID, o.OrderID, o.OrderDate })
.Take(3);
Console.WriteLine("First 3 orders in WA:");
foreach (var order in first3WAOrders)
{
ObjectDumper.Write(order);
}
}//dart
linq21(){
var customers = customersList();
var first3WAOrders = customers
.where((c) => c.region == "WA")
.expand((c) => c.orders
.map((o) => { 'CustomerId': c.customerId, 'OrderId':o.orderId, 'OrderDate':o.orderDate }))
.take(3);
print("First 3 orders in WA:");
first3WAOrders.forEach(print);
}Output
First 3 orders in WA:
{CustomerId: LAZYK, OrderId: 10482, OrderDate: 1997-03-21 00:00:00.000}
{CustomerId: LAZYK, OrderId: 10545, OrderDate: 1997-05-22 00:00:00.000}
{CustomerId: TRAIH, OrderId: 10574, OrderDate: 1997-06-19 00:00:00.000}
linq22: Skip - Simple
//c#
public void Linq22()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var allButFirst4Numbers = numbers.Skip(4);
Console.WriteLine("All but first 4 numbers:");
foreach (var n in allButFirst4Numbers)
{
Console.WriteLine(n);
}
}//dart
linq22(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var allButFirst4Numbers = numbers.skip(4);
print("All but first 4 numbers:");
allButFirst4Numbers.forEach(print);
}Output
All but first 4 numbers:
9
8
6
7
2
0
linq23: Skip - Nested
//c#
public void Linq23()
{
List<Customer> customers = GetCustomerList();
var waOrders =
from c in customers
from o in c.Orders
where c.Region == "WA"
select new { c.CustomerID, o.OrderID, o.OrderDate };
var allButFirst2Orders = waOrders.Skip(2);
Console.WriteLine("All but first 2 orders in WA:");
foreach (var order in allButFirst2Orders)
{
ObjectDumper.Write(order);
}
}//dart
linq23(){
var customers = customersList();
var waOrders = customers
.where((c) => c.region == "WA")
.expand((c) => c.orders
.map((o) => { 'CustomerId': c.customerId, 'OrderId':o.orderId, 'OrderDate':o.orderDate }));
var allButFirst2Orders = waOrders.skip(2);
print("All but first 2 orders in WA:");
allButFirst2Orders.forEach(print);
}Output
All but first 2 orders in WA:
{CustomerId: TRAIH, OrderId: 10574, OrderDate: 1997-06-19 00:00:00.000}
{CustomerId: TRAIH, OrderId: 10577, OrderDate: 1997-06-23 00:00:00.000}
{CustomerId: TRAIH, OrderId: 10822, OrderDate: 1998-01-08 00:00:00.000}
{CustomerId: WHITC, OrderId: 10269, OrderDate: 1996-07-31 00:00:00.000}
{CustomerId: WHITC, OrderId: 10344, OrderDate: 1996-11-01 00:00:00.000}
{CustomerId: WHITC, OrderId: 10469, OrderDate: 1997-03-10 00:00:00.000}
{CustomerId: WHITC, OrderId: 10483, OrderDate: 1997-03-24 00:00:00.000}
{CustomerId: WHITC, OrderId: 10504, OrderDate: 1997-04-11 00:00:00.000}
{CustomerId: WHITC, OrderId: 10596, OrderDate: 1997-07-11 00:00:00.000}
{CustomerId: WHITC, OrderId: 10693, OrderDate: 1997-10-06 00:00:00.000}
{CustomerId: WHITC, OrderId: 10696, OrderDate: 1997-10-08 00:00:00.000}
{CustomerId: WHITC, OrderId: 10723, OrderDate: 1997-10-30 00:00:00.000}
{CustomerId: WHITC, OrderId: 10740, OrderDate: 1997-11-13 00:00:00.000}
{CustomerId: WHITC, OrderId: 10861, OrderDate: 1998-01-30 00:00:00.000}
{CustomerId: WHITC, OrderId: 10904, OrderDate: 1998-02-24 00:00:00.000}
{CustomerId: WHITC, OrderId: 11032, OrderDate: 1998-04-17 00:00:00.000}
{CustomerId: WHITC, OrderId: 11066, OrderDate: 1998-05-01 00:00:00.000}
linq24: TakeWhile - Simple
//c#
public void Linq24()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var firstNumbersLessThan6 = numbers.TakeWhile(n => n < 6);
Console.WriteLine("First numbers less than 6:");
foreach (var n in firstNumbersLessThan6)
{
Console.WriteLine(n);
}
}//dart
linq24(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var firstNumbersLessThan6 = numbers.takeWhile((n) => n < 6);
print("First numbers less than 6:");
firstNumbersLessThan6.forEach(print);
}Output
First numbers less than 6:
5
4
1
3
linq25: TakeWhile - Indexed
//c#
public void Linq25()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var firstSmallNumbers = numbers.TakeWhile((n, index) => n >= index);
Console.WriteLine("First numbers not less than their position:");
foreach (var n in firstSmallNumbers)
{
Console.WriteLine(n);
}
}//dart
linq25(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
int index = 0;
var firstSmallNumbers = numbers.takeWhile((n) => n >= index++);
print("First numbers not less than their position:");
firstSmallNumbers.forEach(print);
}Output
First numbers not less than their position:
5
4
linq26: SkipWhile - Simple
//c#
public void Linq26()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var allButFirst3Numbers = numbers.SkipWhile(n => n % 3 != 0);
Console.WriteLine("All elements starting from first element divisible by 3:");
foreach (var n in allButFirst3Numbers)
{
Console.WriteLine(n);
}
}//dart
linq26(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var allButFirst3Numbers = numbers.skipWhile((n) => n % 3 != 0);
print("All elements starting from first element divisible by 3:");
allButFirst3Numbers.forEach(print);
}Output
All elements starting from first element divisible by 3:
3
9
8
6
7
2
0
linq27: SkipWhile - Indexed
//c#
public void Linq27()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var laterNumbers = numbers.SkipWhile((n, index) => n >= index);
Console.WriteLine("All elements starting from first element less than its position:");
foreach (var n in laterNumbers)
{
Console.WriteLine(n);
}
}//dart
linq27(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
int index = 0;
var laterNumbers = numbers.skipWhile((n) => n >= index++);
print("All elements starting from first element less than its position:");
laterNumbers.forEach(print);
}Output
All elements starting from first element less than its position:
1
3
9
8
6
7
2
0
LINQ - Ordering Operators
C# utils added
public class CaseInsensitiveComparer : IComparer<string>
{
public int Compare(string x, string y)
{
return string.Compare(x, y, StringComparison.OrdinalIgnoreCase);
}
}Dart utils added
wrap(value, fn(x)) => fn(value);
order(List seq, {Comparator by, List<Comparator> byAll, on(x), List<Function> onAll}) =>
by != null ?
(seq..sort(by))
: byAll != null ?
(seq..sort((a,b) => byAll
.firstWhere((compare) => compare(a,b) != 0, orElse:() => (x,y) => 0)(a,b)))
: on != null ?
(seq..sort((a,b) => on(a).compareTo(on(b))))
: onAll != null ?
(seq..sort((a,b) =>
wrap(onAll.firstWhere((_on) => _on(a).compareTo(_on(b)) != 0, orElse:() => (x) => 0),
(_on) => _on(a).compareTo(_on(b))
)))
: (seq..sort());
caseInsensitiveComparer(a,b) =>
a.toUpperCase().compareTo(b.toUpperCase());linq28: OrderBy - Simple 1
//c#
public void Linq28()
{
string[] words = { "cherry", "apple", "blueberry" };
var sortedWords =
from w in words
orderby w
select w;
Console.WriteLine("The sorted list of words:");
foreach (var w in sortedWords)
{
Console.WriteLine(w);
}
}//dart
linq28(){
var words = [ "cherry", "apple", "blueberry" ];
var sortedWords = order(words);
print("The sorted list of words:");
sortedWords.forEach(print);
}Output
The sorted list of words:
apple
blueberry
cherry
linq29: OrderBy - Simple 2
//c#
public void Linq29()
{
string[] words = { "cherry", "apple", "blueberry" };
var sortedWords =
from w in words
orderby w.Length
select w;
Console.WriteLine("The sorted list of words (by length):");
foreach (var w in sortedWords)
{
Console.WriteLine(w);
}
}//dart
linq29(){
var words = [ "cherry", "apple", "blueberry" ];
var sortedWords = order(words, on:(a) => a.length);
print("The sorted list of words (by length):");
sortedWords.forEach(print);
}Output
The sorted list of words (by length):
apple
cherry
blueberry
linq30: OrderBy - Simple 3
//c#
public void Linq30()
{
List<Product> products = GetProductList();
var sortedProducts =
from p in products
orderby p.ProductName
select p;
ObjectDumper.Write(sortedProducts);
}//dart
linq30(){
var products = productsList();
var sortedProducts = order(products, on:(a) => a.productName);
sortedProducts.forEach(print);
}Output
{productId: 17, productName: Alice Mutton, category: Meat/Poultry, unitPrice: 39.0, unitsInStock: 0}
{productId: 3, productName: Aniseed Syrup, category: Condiments, unitPrice: 10.0, unitsInStock: 13}
{productId: 40, productName: Boston Crab Meat, category: Seafood, unitPrice: 18.4, unitsInStock: 123}
{productId: 60, productName: Camembert Pierrot, category: Dairy Products, unitPrice: 34.0, unitsInStock: 19}
{productId: 18, productName: Carnarvon Tigers, category: Seafood, unitPrice: 62.5, unitsInStock: 42}
...
linq31: OrderBy - Comparer
//c#
public void Linq31()
{
string[] words = { "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" };
var sortedWords = words.OrderBy(a => a, new CaseInsensitiveComparer());
ObjectDumper.Write(sortedWords);
} //dart
linq31(){
var words = [ "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" ];
var sortedWords = order(words, by:caseInsensitiveComparer);
sortedWords.forEach(print);
}Output
AbAcUs
aPPLE
BlUeBeRrY
bRaNcH
cHeRry
ClOvEr
linq32: OrderByDescending - Simple 1
//c#
public void Linq32()
{
double[] doubles = { 1.7, 2.3, 1.9, 4.1, 2.9 };
var sortedDoubles =
from d in doubles
orderby d descending
select d;
Console.WriteLine("The doubles from highest to lowest:");
foreach (var d in sortedDoubles)
{
Console.WriteLine(d);
}
}//dart
linq32(){
var doubles = [ 1.7, 2.3, 1.9, 4.1, 2.9 ];
var sortedDoubles = order(doubles).reversed;
print("The doubles from highest to lowest:");
sortedDoubles.forEach(print);
}Output
The doubles from highest to lowest:
4.1
2.9
2.3
1.9
1.7
linq33: OrderByDescending - Simple 2
//c#
public void Linq33()
{
List<Product> products = GetProductList();
var sortedProducts =
from p in products
orderby p.UnitsInStock descending
select p;
ObjectDumper.Write(sortedProducts);
}//dart
linq33(){
var products = productsList();
var sortedProducts = order(products, on:(a) => a.unitsInStock).reversed;
sortedProducts.forEach(print);
}Output
{productId: 75, productName: Rh�nbr�u Klosterbier, category: Beverages, unitPrice: 7.75, unitsInStock: 125}
{productId: 40, productName: Boston Crab Meat, category: Seafood, unitPrice: 18.4, unitsInStock: 123}
{productId: 6, productName: Grandma's Boysenberry Spread, category: Condiments, unitPrice: 25.0, unitsInStock: 120}
{productId: 55, productName: P�t� chinois, category: Meat/Poultry, unitPrice: 24.0, unitsInStock: 115}
{productId: 61, productName: Sirop d'�rable, category: Condiments, unitPrice: 28.5, unitsInStock: 113}
...
linq34: OrderByDescending - Comparer
//c#
public void Linq34()
{
string[] words = { "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" };
var sortedWords = words.OrderByDescending(a => a, new CaseInsensitiveComparer());
ObjectDumper.Write(sortedWords);
} //dart
linq34(){
var words = [ "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" ];
var sortedWords = order(words, by:caseInsensitiveComparer).reversed;
sortedWords.forEach(print);
}Output
ClOvEr
cHeRry
bRaNcH
BlUeBeRrY
aPPLE
AbAcUs
linq35: ThenBy - Simple
//c#
public void Linq35()
{
string[] digits = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
var sortedDigits =
from d in digits
orderby d.Length, d
select d;
Console.WriteLine("Sorted digits:");
foreach (var d in sortedDigits)
{
Console.WriteLine(d);
}
}//dart
linq35(){
var digits = [ "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" ];
var sortedDigits = order(digits, onAll:[(a) => a.length, (a) => a]);
print("Sorted digits:");
sortedDigits.forEach(print);
}Output
Sorted digits:
one
six
two
five
four
nine
zero
eight
seven
three
linq36: ThenBy - Comparer
//c#
public void Linq36()
{
string[] words = { "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" };
var sortedWords =
words.OrderBy(a => a.Length)
.ThenBy(a => a, new CaseInsensitiveComparer());
ObjectDumper.Write(sortedWords);
} //dart
linq36(){
var words = [ "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" ];
var sortedWords = order(words, byAll:[(a,b) => a.length.compareTo(b.length), caseInsensitiveComparer]);
sortedWords.forEach(print);
}Output
aPPLE
AbAcUs
bRaNcH
cHeRry
ClOvEr
BlUeBeRrY
linq37: ThenByDescending - Simple
//c#
public void Linq37()
{
List<Product> products = GetProductList();
var sortedProducts =
from p in products
orderby p.Category, p.UnitPrice descending
select p;
ObjectDumper.Write(sortedProducts);
}//dart
linq37(){
var products = productsList();
var sortedProducts = order(products, onAll:[(a) => a.category, (a) => a.unitPrice * -1]);
sortedProducts.forEach(print);
}Output
{productId: 38, productName: C�te de Blaye, category: Beverages, unitPrice: 263.5, unitsInStock: 17}
{productId: 43, productName: Ipoh Coffee, category: Beverages, unitPrice: 46.0, unitsInStock: 17}
{productId: 2, productName: Chang, category: Beverages, unitPrice: 19.0, unitsInStock: 17}
{productId: 76, productName: Lakkalik��ri, category: Beverages, unitPrice: 18.0, unitsInStock: 57}
{productId: 39, productName: Chartreuse verte, category: Beverages, unitPrice: 18.0, unitsInStock: 69}
{productId: 1, productName: Chai, category: Beverages, unitPrice: 18.0, unitsInStock: 39}
{productId: 35, productName: Steeleye Stout, category: Beverages, unitPrice: 18.0, unitsInStock: 20}
{productId: 70, productName: Outback Lager, category: Beverages, unitPrice: 15.0, unitsInStock: 15}
{productId: 34, productName: Sasquatch Ale, category: Beverages, unitPrice: 14.0, unitsInStock: 111}
...
linq38: ThenByDescending - Comparer
//c#
public void Linq38()
{
string[] words = { "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" };
var sortedWords =
words.OrderBy(a => a.Length)
.ThenByDescending(a => a, new CaseInsensitiveComparer());
ObjectDumper.Write(sortedWords);
} //dart
linq38(){
var words = [ "aPPLE", "AbAcUs", "bRaNcH", "BlUeBeRrY", "ClOvEr", "cHeRry" ];
var sortedWords = order(words,
byAll:[(a,b) => a.length.compareTo(b.length), (a,b) => caseInsensitiveComparer(b,a)]);
sortedWords.forEach(print);
}Output
aPPLE
ClOvEr
cHeRry
bRaNcH
AbAcUs
BlUeBeRrY
linq39: Reverse
//c#
public void Linq39()
{
string[] digits = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
var reversedIDigits = (
from d in digits
where d[1] == 'i'
select d)
.Reverse();
Console.WriteLine("A backwards list of the digits with a second character of 'i':");
foreach (var d in reversedIDigits)
{
Console.WriteLine(d);
}
}//dart
linq39(){
var digits = [ "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" ];
var reversedIDigits = digits
.where((d) => d[1] == 'i')
.toList()
.reversed;
print("A backwards list of the digits with a second character of 'i':");
reversedIDigits.forEach(print);
}Output
A backwards list of the digits with a second character of 'i':
nine
eight
six
five
LINQ - Grouping Operators
C# utils added
public class AnagramEqualityComparer : IEqualityComparer<string>
{
public bool Equals(string x, string y)
{
return getCanonicalString(x) == getCanonicalString(y);
}
public int GetHashCode(string obj)
{
return getCanonicalString(obj).GetHashCode();
}
private string getCanonicalString(string word)
{
char[] wordChars = word.ToCharArray();
Array.Sort<char>(wordChars);
return new string(wordChars);
}
} Dart utils added
anagramEqualityComparer(a, b) =>
new String.fromCharCodes(orderBy(a.codeUnits.toList()))
.compareTo(new String.fromCharCodes(orderBy(b.codeUnits.toList())));
List<Group> group(Iterable seq, {by(x):null, Comparator matchWith:null, valuesAs(x):null}){
var ret = [];
var map = new Map<dynamic, Group>();
seq.forEach((x){
var val = by(x);
var key = matchWith != null
? map.keys.firstWhere((k) => matchWith(val, k) == 0, orElse:() => val)
: val;
if (!map.containsKey(key))
map[key] = new Group(val);
if (valuesAs != null)
x = valuesAs(x);
map[key].add(x);
});
return map.values.toList();
}
class Group extends IterableBase {
var key;
List _list;
Group(this.key) : _list = [];
get iterator => _list.iterator;
void add(e) => _list.add(e);
get values => _list;
}linq40: GroupBy - Simple 1
//c#
public void Linq40()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var numberGroups =
from n in numbers
group n by n % 5 into g
select new { Remainder = g.Key, Numbers = g };
foreach (var g in numberGroups)
{
Console.WriteLine("Numbers with a remainder of {0} when divided by 5:", g.Remainder);
foreach (var n in g.Numbers)
{
Console.WriteLine(n);
}
}
}//dart
linq40(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var numberGroups = group(numbers, by:(n) => n % 5)
.map((g) => {'Remainder':g.key, 'Numbers':g});
numberGroups.forEach((g){
print("Numbers with a remainder of ${g['Remainder']} when divided by 5:");
g['Numbers'].forEach(print);
});
}Output
Numbers with a remainder of 0 when divided by 5:
5
0
Numbers with a remainder of 1 when divided by 5:
1
6
Numbers with a remainder of 2 when divided by 5:
7
2
Numbers with a remainder of 3 when divided by 5:
3
8
Numbers with a remainder of 4 when divided by 5:
4
9
linq41: GroupBy - Simple 2
//c#
public void Linq41()
{
string[] words = { "blueberry", "chimpanzee", "abacus", "banana", "apple", "cheese" };
var wordGroups =
from w in words
group w by w[0] into g
select new { FirstLetter = g.Key, Words = g };
foreach (var g in wordGroups)
{
Console.WriteLine("Words that start with the letter '{0}':", g.FirstLetter);
foreach (var w in g.Words)
{
Console.WriteLine(w);
}
}
}linq41(){
var words = [ "blueberry", "chimpanzee", "abacus", "banana", "apple", "cheese" ];
var wordGroups = group(words, by:(w) => w[0])
.map((g) => { 'FirstLetter': g.key, 'Words': g });
wordGroups.forEach((g){
print("Words that start with the letter '${g['FirstLetter']}':");
g['Words'].forEach(print);
});
}Output
//dart
Words that start with the letter 'c':
chimpanzee
cheese
Words that start with the letter 'a':
abacus
apple
Words that start with the letter 'b':
blueberry
banana
linq42: GroupBy - Simple 3
//c#
public void Linq42()
{
List<Product> products = GetProductList();
var orderGroups =
from p in products
group p by p.Category into g
select new { Category = g.Key, Products = g };
ObjectDumper.Write(orderGroups, 1);
} //dart
linq42(){
var products = productsList();
var orderGroups = group(products, by:(p) => p.category)
.map((g) => { 'Category': g.key, 'Products': g });
orderGroups.forEach(print);
}Output
{Category: Dairy Products, Products: {{productId: 11, productName: Queso Cabrales, category: Dairy Products, unitPrice: 21.0, unitsInStock: 22}, {productId: 12, productName: Queso Manchego La Pastora, category: Dairy Products, unitPrice: 38.0, unitsInStock: 86}, {productId: 31, productName: Gorgonzola Telino, category: Dairy Products, unitPrice: 12.5, unitsInStock: 0}, {productId: 32, productName: Mascarpone Fabioli, category: Dairy Products, unitPrice: 32.0, unitsInStock: 9}, {productId: 33, productName: Geitost, category: Dairy Products, unitPrice: 2.5, unitsInStock: 112}, {productId: 59, productName: Raclette Courdavault, category: Dairy Products, unitPrice: 55.0, unitsInStock: 79}, {productId: 60, productName: Camembert Pierrot, category: Dairy Products, unitPrice: 34.0, unitsInStock: 19}, {productId: 69, productName: Gudbrandsdalsost, category: Dairy Products, unitPrice: 36.0, unitsInStock: 26}, {productId: 71, productName: Flotemysost, category: Dairy Products, unitPrice: 21.5, unitsInStock: 26}, {productId: 72, productName: Mozzarella di Giovanni, category: Dairy Products, unitPrice: 34.8, unitsInStock: 14}}}
{Category: Grains/Cereals, Products: {{productId: 22, productName: Gustaf's Kn�ckebr�d, category: Grains/Cereals, unitPrice: 21.0, unitsInStock: 104}, {productId: 23, productName: Tunnbr�d, category: Grains/Cereals, unitPrice: 9.0, unitsInStock: 61}, {productId: 42, productName: Singaporean Hokkien Fried Mee, category: Grains/Cereals, unitPrice: 14.0, unitsInStock: 26}, {productId: 52, productName: Filo Mix, category: Grains/Cereals, unitPrice: 7.0, unitsInStock: 38}, {productId: 56, productName: Gnocchi di nonna Alice, category: Grains/Cereals, unitPrice: 38.0, unitsInStock: 21}, {productId: 57, productName: Ravioli Angelo, category: Grains/Cereals, unitPrice: 19.5, unitsInStock: 36}, {productId: 64, productName: Wimmers gute Semmelkn�del, category: Grains/Cereals, unitPrice: 33.25, unitsInStock: 22}}}
linq43: GroupBy - Nested
//c#
public void Linq43()
{
List<Customer> customers = GetCustomerList();
var customerOrderGroups =
from c in customers
select
new
{
c.CompanyName,
YearGroups =
from o in c.Orders
group o by o.OrderDate.Year into yg
select
new
{
Year = yg.Key,
MonthGroups =
from o in yg
group o by o.OrderDate.Month into mg
select new { Month = mg.Key, Orders = mg }
}
};
ObjectDumper.Write(customerOrderGroups, 3);
} //dart
linq43(){
var customers = customersList();
var customerOrderGroups = customers
.map((c) => {
'CompanyName': c.companyName,
'YearGroups': group(c.orders, by:(o) => o.orderDate.year)
.map((yg) => {
'Year': yg.key,
'MonthGroups': group(yg, by:(o) => o.orderDate.month)
.map((mg) => { 'Month': mg.key, 'Orders': mg })
})
});
customerOrderGroups.forEach(print);
}Output
{CompanyName: Alfreds Futterkiste, YearGroups: {{Year: 1997, MonthGroups: {{Month: 8, Orders: {{orderId: 10643, orderDate: 1997-08-25 00:00:00.000, total: 814.5}}}, {Month: 10, Orders: {{orderId: 10692, orderDate: 1997-10-03 00:00:00.000, total: 878.0}, {orderId: 10702, orderDate: 1997-10-13 00:00:00.000, total: 330.0}}}}}, {Year: 1998, MonthGroups: {{Month: 1, Orders: {{orderId: 10835, orderDate: 1998-01-15 00:00:00.000, total: 845.8}}}, {Month: 3, Orders: {{orderId: 10952, orderDate: 1998-03-16 00:00:00.000, total: 471.2}}}, {Month: 4, Orders: {{orderId: 11011, orderDate: 1998-04-09 00:00:00.000, total: 933.5}}}}}}}
{CompanyName: Ana Trujillo Emparedados y helados, YearGroups: {{Year: 1996, MonthGroups: {{Month: 9, Orders: {{orderId: 10308, orderDate: 1996-09-18 00:00:00.000, total: 88.8}}}}}, {Year: 1997, MonthGroups: {{Month: 8, Orders: {{orderId: 10625, orderDate: 1997-08-08 00:00:00.000, total: 479.75}}}, {Month: 11, Orders: {{orderId: 10759, orderDate: 1997-11-28 00:00:00.000, total: 320.0}}}}}, {Year: 1998, MonthGroups: {{Month: 3, Orders: {{orderId: 10926, orderDate: 1998-03-04 00:00:00.000, total: 514.4}}}}}}}
linq44: GroupBy - Comparer
//c#
public void Linq44()
{
string[] anagrams = { "from ", " salt", " earn ", " last ", " near ", " form " };
var orderGroups = anagrams.GroupBy(w => w.Trim(), new AnagramEqualityComparer());
ObjectDumper.Write(orderGroups, 1);
} //dart
linq44(){
var anagrams = [ "from ", " salt", " earn ", " last ", " near ", " form " ];
var orderGroups = group(anagrams, by:(w) => w.trim(), matchWith:anagramEqualityComparer);
orderGroups.forEach((x) => print(x.values));
}Output
[ salt, last ]
[ earn , near ]
[from , form ]
linq45: GroupBy - Comparer, Mapped
//c#
public void Linq45()
{
string[] anagrams = { "from ", " salt", " earn ", " last ", " near ", " form " };
var orderGroups = anagrams.GroupBy(
w => w.Trim(),
a => a.ToUpper(),
new AnagramEqualityComparer()
);
ObjectDumper.Write(orderGroups, 1);
} //dart
linq45(){
var anagrams = [ "from ", " salt", " earn ", " last ", " near ", " form " ];
var orderGroups = group(anagrams,
by: (w) => w.trim(),
matchWith: anagramEqualityComparer,
valuesAs: (w) => w.toUpperCase());
orderGroups.forEach((x) => print(x.values));
}Output
[ SALT, LAST ]
[ EARN , NEAR ]
[FROM , FORM ]
LINQ - Set Operators
linq46: Distinct - 1
//c#
public void Linq46()
{
int[] factorsOf300 = { 2, 2, 3, 5, 5 };
var uniqueFactors = factorsOf300.Distinct();
Console.WriteLine("Prime factors of 300:");
foreach (var f in uniqueFactors)
{
Console.WriteLine(f);
}
}//dart
linq46(){
var factorsOf300 = [ 2, 2, 3, 5, 5 ];
var uniqueFactors = factorsOf300.toSet();
print("Prime factors of 300:");
uniqueFactors.forEach(print);
}Output
Prime factors of 300:
2
3
5
linq47: Distinct - 2
//c#
public void Linq47()
{
List<Product> products = GetProductList();
var categoryNames = (
from p in products
select p.Category)
.Distinct();
Console.WriteLine("Category names:");
foreach (var n in categoryNames)
{
Console.WriteLine(n);
}
}//dart
linq47(){
var products = productsList();
var categoryNames = products
.map((p) => p.category)
.toSet();
print("Category names:");
categoryNames.forEach(print);
}Output
Category names:
Dairy Products
Grains/Cereals
Confections
Seafood
Condiments
Meat/Poultry
Produce
Beverages
linq48: Union - 1
//c#
public void Linq48()
{
int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
int[] numbersB = { 1, 3, 5, 7, 8 };
var uniqueNumbers = numbersA.Union(numbersB);
Console.WriteLine("Unique numbers from both arrays:");
foreach (var n in uniqueNumbers)
{
Console.WriteLine(n);
}
}//dart
linq48(){
var numbersA = [ 0, 2, 4, 5, 6, 8, 9 ];
var numbersB = [ 1, 3, 5, 7, 8 ];
var uniqueNumbers = numbersA.toSet().union(numbersB.toSet());
print("Unique numbers from both arrays:");
uniqueNumbers.forEach(print);
}Output
Unique numbers from both arrays:
0
1
2
3
4
5
6
7
8
9
linq49: Union - 2
//c#
public void Linq49()
{
List<Product> products = GetProductList();
List<Customer> customers = GetCustomerList();
var productFirstChars =
from p in products
select p.ProductName[0];
var customerFirstChars =
from c in customers
select c.CompanyName[0];
var uniqueFirstChars = productFirstChars.Union(customerFirstChars);
Console.WriteLine("Unique first letters from Product names and Customer names:");
foreach (var ch in uniqueFirstChars)
{
Console.WriteLine(ch);
}
}//dart
linq49(){
var products = productsList();
var customers = customersList();
var productFirstChars = products
.map((p) => p.productName[0]);
var customerFirstChars = customers
.map((c) => c.companyName[0]);
var uniqueFirstChars = productFirstChars.toSet().union(customerFirstChars.toSet());
print("Unique first letters from Product names and Customer names:");
uniqueFirstChars.forEach(print);
}Output
Unique first letters from Product names and Customer names:
S
F
T
N
K
E
V
Z
Q
M
C
L
A
J
W
P
B
O
H
D
R
I
G
U
linq50: Intersect - 1
//c#
public void Linq50()
{
int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
int[] numbersB = { 1, 3, 5, 7, 8 };
var commonNumbers = numbersA.Intersect(numbersB);
Console.WriteLine("Common numbers shared by both arrays:");
foreach (var n in commonNumbers)
{
Console.WriteLine(n);
}
}//dart
linq50(){
var numbersA = [ 0, 2, 4, 5, 6, 8, 9 ];
var numbersB = [ 1, 3, 5, 7, 8 ];
var commonNumbers = numbersA.toSet().intersection(numbersB.toSet());
print("Common numbers shared by both arrays:");
commonNumbers.forEach(print);
}Output
Common numbers shared by both arrays:
8
5
linq51: Intersect - 2
//c#
public void Linq51()
{
List<Product> products = GetProductList();
List<Customer> customers = GetCustomerList();
var productFirstChars =
from p in products
select p.ProductName[0];
var customerFirstChars =
from c in customers
select c.CompanyName[0];
var commonFirstChars = productFirstChars.Intersect(customerFirstChars);
Console.WriteLine("Common first letters from Product names and Customer names:");
foreach (var ch in commonFirstChars)
{
Console.WriteLine(ch);
}
}//dart
linq51(){
var products = productsList();
var customers = customersList();
var productFirstChars = products
.map((p) => p.productName[0]);
var customerFirstChars = customers
.map((c) => c.companyName[0]);
var commonFirstChars = productFirstChars.toSet().intersection(customerFirstChars.toSet());
print("Common first letters from Product names and Customer names:");
commonFirstChars.forEach(print);
}Output
Common first letters from Product names and Customer names:
F
S
T
N
K
E
V
Q
M
C
L
A
O
W
P
B
I
G
R
linq52: Except - 1
//c#
public void Linq52()
{
int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
int[] numbersB = { 1, 3, 5, 7, 8 };
IEnumerable<int> aOnlyNumbers = numbersA.Except(numbersB);
Console.WriteLine("Numbers in first array but not second array:");
foreach (var n in aOnlyNumbers)
{
Console.WriteLine(n);
}
}//dart
linq52(){
var numbersA = [ 0, 2, 4, 5, 6, 8, 9 ];
var numbersB = [ 1, 3, 5, 7, 8 ];
var aOnlyNumbers = numbersA.toSet().difference(numbersB.toSet());
print("Numbers in first array but not second array:");
aOnlyNumbers.forEach(print);
}Output
Numbers in first array but not second array:
0
9
2
4
6
linq53: Except - 2
//c#
public void Linq53()
{
List<Product> products = GetProductList();
List<Customer> customers = GetCustomerList();
var productFirstChars =
from p in products
select p.ProductName[0];
var customerFirstChars =
from c in customers
select c.CompanyName[0];
var productOnlyFirstChars = productFirstChars.Except(customerFirstChars);
Console.WriteLine("First letters from Product names, but not from Customer names:");
foreach (var ch in productOnlyFirstChars)
{
Console.WriteLine(ch);
}
}//dart
linq53(){
var products = productsList();
var customers = customersList();
var productFirstChars = products
.map((p) => p.productName[0]);
var customerFirstChars = customers
.map((c) => c.companyName[0]);
var productOnlyFirstChars = productFirstChars.toSet().difference(customerFirstChars.toSet());
print("First letters from Product names, but not from Customer names:");
productOnlyFirstChars.forEach(print);
}Output
First letters from Product names, but not from Customer names:
Z
J
U
LINQ - Conversion Operators
Dart utils added
toMap(List seq, f(x)){
var map = {};
seq.forEach((x) => map[f(x)] = x);
return map;
}
ofType(List seq, type) =>
seq.where((x) => reflect(x).type.qualifiedName == reflectClass(type).qualifiedName);linq54: ToArray
//c#
public void Linq54()
{
double[] doubles = { 1.7, 2.3, 1.9, 4.1, 2.9 };
var sortedDoubles =
from d in doubles
orderby d descending
select d;
var doublesArray = sortedDoubles.ToArray();
Console.WriteLine("Every other double from highest to lowest:");
for (int d = 0; d < doublesArray.Length; d += 2)
{
Console.WriteLine(doublesArray[d]);
}
}//dart
linq54(){
var doubles = [ 1.7, 2.3, 1.9, 4.1, 2.9 ];
var sortedDoubles = order(doubles).reversed;
var doublesArray = sortedDoubles.toList(growable:false);
print("Every other double from highest to lowest:");
for (int d = 0; d < doublesArray.length; d += 2){
print(doublesArray[d]);
}
}Output
Every other double from highest to lowest:
4.1
2.3
1.7
linq55: ToList
//c#
public void Linq55()
{
string[] words = { "cherry", "apple", "blueberry" };
var sortedWords =
from w in words
orderby w
select w;
var wordList = sortedWords.ToList();
Console.WriteLine("The sorted word list:");
foreach (var w in wordList)
{
Console.WriteLine(w);
}
}//dart
linq55(){
var words = [ "cherry", "apple", "blueberry" ];
var sortedWords = orderBy(words);
var wordList = sortedWords.toList();
print("The sorted word list:");
wordList.forEach(print);
}Output
The sorted word list:
apple
blueberry
cherry
linq56: ToDictionary
//c#
public void Linq56()
{
var scoreRecords = new[] { new {Name = "Alice", Score = 50},
new {Name = "Bob" , Score = 40},
new {Name = "Cathy", Score = 45}
};
var scoreRecordsDict = scoreRecords.ToDictionary(sr => sr.Name);
Console.WriteLine("Bob's score: {0}", scoreRecordsDict["Bob"]);
}//dart
linq56(){
var scoreRecords = [{ 'Name': "Alice", 'Score': 50},
{ 'Name': "Bob" , 'Score': 40},
{ 'Name': "Cathy", 'Score': 45}];
var scoreRecordsDict = toMap(scoreRecords, (sr) => sr['Name']);
print("Bob's score: ${scoreRecordsDict['Bob']}");
}Output
Bob's score: {Name: Bob, Score: 40}
linq57: OfType
//c#
public void Linq57()
{
object[] numbers = { null, 1.0, "two", 3, "four", 5, "six", 7.0 };
var doubles = numbers.OfType<double>();
Console.WriteLine("Numbers stored as doubles:");
foreach (var d in doubles)
{
Console.WriteLine(d);
}
}//dart
linq57(){
var numbers = [ null, 1.0, "two", 3, "four", 5, "six", 7.0 ];
var doubles = ofType(numbers, double);
print("Numbers stored as doubles:");
doubles.forEach(print);
}Output
Numbers stored as doubles:
1.0
7.0
LINQ - Element Operators
linq58: First - Simple
//c#
public void Linq58()
{
List<Product> products = GetProductList();
Product product12 = (
from p in products
where p.ProductID == 12
select p)
.First();
ObjectDumper.Write(product12);
}//dart
linq58(){
var products = productsList();
var product12 = products
.where((p) => p.productId == 12)
.first;
print(product12);
}Output
{productId: 12, productName: Queso Manchego La Pastora, category: Dairy Products, unitPrice: 38.0, unitsInStock: 86}
linq59: First - Condition
//c#
public void Linq59()
{
string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
string startsWithO = strings.First(s => s[0] == 'o');
Console.WriteLine("A string starting with 'o': {0}", startsWithO);
}//dart
linq59(){
var strings = [ "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" ];
var startsWithO = strings.firstWhere((s) => s[0] == 'o');
print("A string starting with 'o': $startsWithO");
}Output
A string starting with 'o': one
linq61: FirstOrDefault - Simple
//c#
public void Linq61()
{
int[] numbers = { };
int firstNumOrDefault = numbers.FirstOrDefault();
Console.WriteLine(firstNumOrDefault);
}//dart
linq61(){
var numbers = [];
int firstNumOrDefault = numbers.firstWhere((x) => true, orElse:() => 0);
print(firstNumOrDefault);
}Output
0
linq62: FirstOrDefault - Condition
//c#
public void Linq62()
{
List<Product> products = GetProductList();
Product product789 = products.FirstOrDefault(p => p.ProductID == 789);
Console.WriteLine("Product 789 exists: {0}", product789 != null);
}//dart
linq62(){
var products = productsList();
var product789 = products.firstWhere((p) => p.productId == 789, orElse:() => null);
print("Product 789 exists: ${product789 != null}");
}Output
Product 789 exists: false
linq64: ElementAt
//c#
public void Linq64()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
int fourthLowNum = (
from n in numbers
where n > 5
select n)
.ElementAt(1); // second number is index 1 because sequences use 0-based indexing
Console.WriteLine("Second number > 5: {0}", fourthLowNum);
}//dart
linq64(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
int fourthLowNum = numbers
.where((n) => n > 5)
.elementAt(1);
print("Second number > 5: $fourthLowNum");
}Output
Second number > 5: 8
LINQ - Generation Operators
Dart utils added
List range(int from, [int to]) =>
to != null
? new List.generate(to, (x) => x + from)
: new List.generate(from, (x) => x);linq65: Range
//c#
public void Linq65()
{
var numbers =
from n in Enumerable.Range(100, 50)
select new { Number = n, OddEven = n % 2 == 1 ? "odd" : "even" };
foreach (var n in numbers)
{
Console.WriteLine("The number {0} is {1}.", n.Number, n.OddEven);
}
}//dart
linq65(){
var numbers = range(100, 50)
.map((n) => { 'Number': n, 'OddEven': n % 2 == 1 ? "odd" : "even" });
numbers.forEach((n) =>
print("The number ${n['Number']} is ${n['OddEven']}."));
}Output
The number 100 is even.
The number 101 is odd.
The number 102 is even.
The number 103 is odd.
The number 104 is even.
The number 105 is odd.
The number 106 is even.
The number 107 is odd.
The number 108 is even.
The number 109 is odd.
The number 110 is even.
...
linq66: Repeat
//c#
public void Linq66()
{
var numbers = Enumerable.Repeat(7, 10);
foreach (var n in numbers)
{
Console.WriteLine(n);
}
}//dart
linq66(){
var numbers = new List.filled(10, 7);
numbers.forEach(print);
}Output
7
7
7
7
7
7
7
7
7
7
LINQ - Quantifiers
linq67: Any - Simple
//c#
public void Linq67()
{
string[] words = { "believe", "relief", "receipt", "field" };
bool iAfterE = words.Any(w => w.Contains("ei"));
Console.WriteLine("There is a word that contains in the list that contains 'ei': {0}", iAfterE);
}//dart
linq67(){
var words = [ "believe", "relief", "receipt", "field" ];
bool iAfterE = words.any((w) => w.contains("ei"));
print("There is a word that contains in the list that contains 'ei': $iAfterE");
}Output
There is a word that contains in the list that contains 'ei': true
linq69: Any - Grouped
//c#
public void Linq69()
{
List<Product> products = GetProductList();
var productGroups =
from p in products
group p by p.Category into g
where g.Any(p => p.UnitsInStock == 0)
select new { Category = g.Key, Products = g };
ObjectDumper.Write(productGroups, 1);
}//dart
linq69(){
var products = productsList();
var productGroups = group(products, by:(p) => p.category)
.where((g) => g.values.any((p) => p.unitsInStock == 0))
.map((g) => { 'Category': g.key, 'Products': g });
productGroups.forEach(print);
}Output
{Category: Condiments, Products: {{productId: 3, productName: Aniseed Syrup, category: Condiments, unitPrice: 10.0, unitsInStock: 13}, {productId: 4, productName: Chef Anton's Cajun Seasoning, category: Condiments, unitPrice: 22.0, unitsInStock: 53}, {productId: 5, productName: Chef Anton's Gumbo Mix, category: Condiments, unitPrice: 21.35, unitsInStock: 0}, {productId: 6, productName: Grandma's Boysenberry Spread, category: Condiments, unitPrice: 25.0, unitsInStock: 120}, {productId: 8, productName: Northwoods Cranberry Sauce, category: Condiments, unitPrice: 40.0, unitsInStock: 6}, {productId: 15, productName: Genen Shouyu, category: Condiments, unitPrice: 15.5, unitsInStock: 39}, {productId: 44, productName: Gula Malacca, category: Condiments, unitPrice: 19.45, unitsInStock: 27}, {productId: 61, productName: Sirop d'�rable, category: Condiments, unitPrice: 28.5, unitsInStock: 113}, {productId: 63, productName: Vegie-spread, category: Condiments, unitPrice: 43.9, unitsInStock: 24}, {productId: 65, productName: Louisiana Fiery Hot Pepper Sauce, category: Condiments, unitPrice: 21.05, unitsInStock: 76}, {productId: 66, productName: Louisiana Hot Spiced Okra, category: Condiments, unitPrice: 17.0, unitsInStock: 4}, {productId: 77, productName: Original Frankfurter gr�ne So�e, category: Condiments, unitPrice: 13.0, unitsInStock: 32}}}
...
linq70: All - Simple
//c#
public void Linq70()
{
int[] numbers = { 1, 11, 3, 19, 41, 65, 19 };
bool onlyOdd = numbers.All(n => n % 2 == 1);
Console.WriteLine("The list contains only odd numbers: {0}", onlyOdd);
}//dart
linq70(){
var numbers = [ 1, 11, 3, 19, 41, 65, 19 ];
bool onlyOdd = numbers.every((n) => n % 2 == 1);
print("The list contains only odd numbers: $onlyOdd");
}Output
The list contains only odd numbers: true
linq72: All - Grouped
//c#
public void Linq72()
{
List<Product> products = GetProductList();
var productGroups =
from p in products
group p by p.Category into g
where g.All(p => p.UnitsInStock > 0)
select new { Category = g.Key, Products = g };
ObjectDumper.Write(productGroups, 1);
}//dart
linq72(){
var products = productsList();
var productGroups = group(products, by:(p) => p.category)
.where((g) => g.values.every((p) => p.unitsInStock > 0))
.map((g) => { 'Category': g.key, 'Products': g });
productGroups.forEach(print);
}Output
{Category: Grains/Cereals, Products: {{productId: 22, productName: Gustaf's Kn�ckebr�d, category: Grains/Cereals, unitPrice: 21.0, unitsInStock: 104}, {productId: 23, productName: Tunnbr�d, category: Grains/Cereals, unitPrice: 9.0, unitsInStock: 61}, {productId: 42, productName: Singaporean Hokkien Fried Mee, category: Grains/Cereals, unitPrice: 14.0, unitsInStock: 26}, {productId: 52, productName: Filo Mix, category: Grains/Cereals, unitPrice: 7.0, unitsInStock: 38}, {productId: 56, productName: Gnocchi di nonna Alice, category: Grains/Cereals, unitPrice: 38.0, unitsInStock: 21}, {productId: 57, productName: Ravioli Angelo, category: Grains/Cereals, unitPrice: 19.5, unitsInStock: 36}, {productId: 64, productName: Wimmers gute Semmelkn�del, category: Grains/Cereals, unitPrice: 33.25, unitsInStock: 22}}}
...
LINQ - Aggregate Operators
Dart utils added
sum(Iterable seq, [fn(x)]) =>
seq.fold(0, (prev, element) => prev + (fn != null ? fn(element) : element));
min(Iterable seq) =>
seq.fold(double.MAX_FINITE, (prev, element) => prev.compareTo(element) > 0 ? element : prev);
max(Iterable seq) =>
seq.fold(double.MIN_POSITIVE, (prev, element) => prev.compareTo(element) > 0 ? prev : element);
avg(Iterable seq) => sum(seq) / seq.length;linq73: Count - Simple
//c#
public void Linq73()
{
int[] factorsOf300 = { 2, 2, 3, 5, 5 };
int uniqueFactors = factorsOf300.Distinct().Count();
Console.WriteLine("There are {0} unique factors of 300.", uniqueFactors);
}//dart
linq73(){
var factorsOf300 = [ 2, 2, 3, 5, 5 ];
int uniqueFactors = factorsOf300.toSet().length;
print("There are $uniqueFactors unique factors of 300.");
}Output
There are 3 unique factors of 300.
linq74: Count - Conditional
//c#
public void Linq74()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
int oddNumbers = numbers.Count(n => n % 2 == 1);
Console.WriteLine("There are {0} odd numbers in the list.", oddNumbers);
}//dart
linq74(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
int oddNumbers = numbers.where((n) => n % 2 == 1).length;
print("There are $oddNumbers odd numbers in the list.");
}Output
There are 5 odd numbers in the list.
linq76: Count - Nested
//c#
public void Linq76()
{
List<Customer> customers = GetCustomerList();
var orderCounts =
from c in customers
select new { c.CustomerID, OrderCount = c.Orders.Count() };
ObjectDumper.Write(orderCounts);
}//dart
linq76(){
var customers = customersList();
var orderCounts = customers
.map((c) => { 'CustomerId': c.customerId, 'OrderCount': c.orders.length });
orderCounts.forEach(print);
}Output
{CustomerId: ALFKI, OrderCount: 6}
{CustomerId: ANATR, OrderCount: 4}
{CustomerId: ANTON, OrderCount: 7}
{CustomerId: AROUT, OrderCount: 13}
{CustomerId: BERGS, OrderCount: 18}
{CustomerId: BLAUS, OrderCount: 7}
{CustomerId: BLONP, OrderCount: 11}
...
linq77: Count - Grouped
//c#
public void Linq77()
{
List<Product> products = GetProductList();
var categoryCounts =
from p in products
group p by p.Category into g
select new { Category = g.Key, ProductCount = g.Count() };
ObjectDumper.Write(categoryCounts
}//dart
linq77(){
var products = productsList();
var categoryCounts = group(products, by:(p) => p.category)
.map((g) => { 'Category': g.key, 'ProductCount': g.length });
categoryCounts.forEach(print);
}Output
{Category: Dairy Products, ProductCount: 10}
{Category: Grains/Cereals, ProductCount: 7}
{Category: Confections, ProductCount: 13}
{Category: Seafood, ProductCount: 12}
{Category: Condiments, ProductCount: 12}
{Category: Meat/Poultry, ProductCount: 6}
{Category: Produce, ProductCount: 5}
{Category: Beverages, ProductCount: 12}
linq78: Sum - Simple
//c#
public void Linq78()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
double numSum = numbers.Sum();
Console.WriteLine("The sum of the numbers is {0}.", numSum);
}//dart
linq78(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var numSum = sum(numbers);
print("The sum of the numbers is $numSum.");
}Output
The sum of the numbers is 45.
linq79: Sum - Projection
//c#
public void Linq79()
{
string[] words = { "cherry", "apple", "blueberry" };
double totalChars = words.Sum(w => w.Length);
Console.WriteLine("There are a total of {0} characters in these words.", totalChars);
}//dart
linq79(){
var words = [ "cherry", "apple", "blueberry" ];
var totalChars = sum(words, (w) => w.length);
print("There are a total of $totalChars characters in these words.");
}Output
There are a total of 20 characters in these words.
linq80: Sum - Grouped
//c#
public void Linq80()
{
List<Product> products = GetProductList();
var categories =
from p in products
group p by p.Category into g
select new { Category = g.Key, TotalUnitsInStock = g.Sum(p => p.UnitsInStock) };
ObjectDumper.Write(categories);
}//dart
linq80(){
var products = productsList();
var categories = group(products, by:(p) => p.category)
.map((g) => { 'Category': g.key, 'TotalUnitsInStock': sum(g.values, (p) => p.unitsInStock) });
categories.forEach(print);
}Output
{Category: Dairy Products, TotalUnitsInStock: 393}
{Category: Grains/Cereals, TotalUnitsInStock: 308}
{Category: Confections, TotalUnitsInStock: 386}
{Category: Seafood, TotalUnitsInStock: 701}
{Category: Condiments, TotalUnitsInStock: 507}
{Category: Meat/Poultry, TotalUnitsInStock: 165}
{Category: Produce, TotalUnitsInStock: 100}
{Category: Beverages, TotalUnitsInStock: 559}
linq81: Min - Simple
//c#
public void Linq81()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
int minNum = numbers.Min();
Console.WriteLine("The minimum number is {0}.", minNum);
}//dart
linq81(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
int minNum = min(numbers);
print("The minimum number is $minNum.");
}Output
The minimum number is 0.
linq82: Min - Projection
//c#
public void Linq82()
{
string[] words = { "cherry", "apple", "blueberry" };
int shortestWord = words.Min(w => w.Length);
Console.WriteLine("The shortest word is {0} characters long.", shortestWord);
}//dart
linq82(){
var words = [ "cherry", "apple", "blueberry" ];
var shortestWord = min(words.map((x) => x.length));
print("The shortest word is $shortestWord characters long.");
}Output
The shortest word is 5 characters long.
linq83: Min - Grouped
//c#
public void Linq83()
{
List<Product> products = GetProductList();
var categories =
from p in products
group p by p.Category into g
select new { Category = g.Key, CheapestPrice = g.Min(p => p.UnitPrice) };
ObjectDumper.Write(categories);
}//dart
linq83(){
var products = productsList();
var categories = group(products, by:(p) => p.category)
.map((g) => { 'Category': g.key, 'CheapestPrice': min(g.values.map((p) => p.unitPrice)) });
categories.forEach(print);
}Output
{Category: Dairy Products, CheapestPrice: 2.5}
{Category: Grains/Cereals, CheapestPrice: 7.0}
{Category: Confections, CheapestPrice: 9.2}
{Category: Seafood, CheapestPrice: 6.0}
{Category: Condiments, CheapestPrice: 10.0}
{Category: Meat/Poultry, CheapestPrice: 7.45}
{Category: Produce, CheapestPrice: 10.0}
{Category: Beverages, CheapestPrice: 4.5}
linq84: Min - Elements
//c#
public void Linq84()
{
List<Product> products = GetProductList();
var categories =
from p in products
group p by p.Category into g
let minPrice = g.Min(p => p.UnitPrice)
select new { Category = g.Key, CheapestProducts = g.Where(p => p.UnitPrice == minPrice) };
ObjectDumper.Write(categories, 1);
}//dart
linq84(){
var products = productsList();
var categories = group(products, by:(p) => p.category)
.map((g){
var minPrice = min(g.values.map((p) => p.unitPrice));
return { 'Category': g.key, 'CheapestProducts': g.values.where((p) => p.unitPrice == minPrice) };
});
categories.forEach(print);
}Output
{Category: Dairy Products, CheapestProducts: {{productId: 33, productName: Geitost, category: Dairy Products, unitPrice: 2.5, unitsInStock: 112}}}
{Category: Grains/Cereals, CheapestProducts: {{productId: 52, productName: Filo Mix, category: Grains/Cereals, unitPrice: 7.0, unitsInStock: 38}}}
{Category: Confections, CheapestProducts: {{productId: 19, productName: Teatime Chocolate Biscuits, category: Confections, unitPrice: 9.2, unitsInStock: 25}}}
{Category: Seafood, CheapestProducts: {{productId: 13, productName: Konbu, category: Seafood, unitPrice: 6.0, unitsInStock: 24}}}
{Category: Condiments, CheapestProducts: {{productId: 3, productName: Aniseed Syrup, category: Condiments, unitPrice: 10.0, unitsInStock: 13}}}
{Category: Meat/Poultry, CheapestProducts: {{productId: 54, productName: Tourti�re, category: Meat/Poultry, unitPrice: 7.45, unitsInStock: 21}}}
{Category: Produce, CheapestProducts: {{productId: 74, productName: Longlife Tofu, category: Produce, unitPrice: 10.0, unitsInStock: 4}}}
{Category: Beverages, CheapestProducts: {{productId: 24, productName: Guaran� Fant�stica, category: Beverages, unitPrice: 4.5, unitsInStock: 20}}}
linq85: Max - Simple
//c#
public void Linq85()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
int maxNum = numbers.Max();
Console.WriteLine("The maximum number is {0}.", maxNum);
}//dart
linq85(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var maxNum = max(numbers);
print("The maximum number is $maxNum.");
}Output
The maximum number is 9.
linq86: Max - Projection
//c#
public void Linq86()
{
string[] words = { "cherry", "apple", "blueberry" };
int longestLength = words.Max(w => w.Length);
Console.WriteLine("The longest word is {0} characters long.", longestLength);
}//dart
linq86(){
var words = [ "cherry", "apple", "blueberry" ];
int longestLength = max(words.map((w) => w.length));
print("The longest word is $longestLength characters long.");
}Output
The longest word is 9 characters long.
linq87: Max - Grouped
//c#
public void Linq87()
{
List<Product> products = GetProductList();
var categories =
from p in products
group p by p.Category into g
select new { Category = g.Key, MostExpensivePrice = g.Max(p => p.UnitPrice) };
ObjectDumper.Write(categories);
}//dart
linq87(){
var products = productsList();
var categories = group(products, by:(p) => p.category)
.map((g) => { 'Category': g.key, 'MostExpensivePrice': max(g.values.map((p) => p.unitPrice)) });
categories.forEach(print);
}Output
{Category: Dairy Products, MostExpensivePrice: 55.0}
{Category: Grains/Cereals, MostExpensivePrice: 38.0}
{Category: Confections, MostExpensivePrice: 81.0}
{Category: Seafood, MostExpensivePrice: 62.5}
{Category: Condiments, MostExpensivePrice: 43.9}
{Category: Meat/Poultry, MostExpensivePrice: 123.79}
{Category: Produce, MostExpensivePrice: 53.0}
{Category: Beverages, MostExpensivePrice: 263.5}
linq88: Max - Elements
//c#
public void Linq88()
{
List<Product> products = GetProductList();
var categories =
from p in products
group p by p.Category into g
let maxPrice = g.Max(p => p.UnitPrice)
select new { Category = g.Key, MostExpensiveProducts = g.Where(p => p.UnitPrice == maxPrice) };
ObjectDumper.Write(categories, 1);
}//dart
linq88(){
var products = productsList();
var categories = group(products, by:(p) => p.category)
.map((g){
var maxPrice = max(g.values.map((p) => p.unitPrice));
return { 'Category': g.key, 'MostExpensiveProducts': g.values.where((p) => p.unitPrice == maxPrice) };
});
categories.forEach(print);
}Output
{Category: Dairy Products, MostExpensiveProducts: {{productId: 59, productName: Raclette Courdavault, category: Dairy Products, unitPrice: 55.0, unitsInStock: 79}}}
{Category: Grains/Cereals, MostExpensiveProducts: {{productId: 56, productName: Gnocchi di nonna Alice, category: Grains/Cereals, unitPrice: 38.0, unitsInStock: 21}}}
{Category: Confections, MostExpensiveProducts: {{productId: 20, productName: Sir Rodney's Marmalade, category: Confections, unitPrice: 81.0, unitsInStock: 40}}}
{Category: Seafood, MostExpensiveProducts: {{productId: 18, productName: Carnarvon Tigers, category: Seafood, unitPrice: 62.5, unitsInStock: 42}}}
{Category: Condiments, MostExpensiveProducts: {{productId: 63, productName: Vegie-spread, category: Condiments, unitPrice: 43.9, unitsInStock: 24}}}
{Category: Meat/Poultry, MostExpensiveProducts: {{productId: 29, productName: Th�ringer Rostbratwurst, category: Meat/Poultry, unitPrice: 123.79, unitsInStock: 0}}}
{Category: Produce, MostExpensiveProducts: {{productId: 51, productName: Manjimup Dried Apples, category: Produce, unitPrice: 53.0, unitsInStock: 20}}}
{Category: Beverages, MostExpensiveProducts: {{productId: 38, productName: C�te de Blaye, category: Beverages, unitPrice: 263.5, unitsInStock: 17}}}
linq89: Average - Simple
//c#
public void Linq89()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
double averageNum = numbers.Average();
Console.WriteLine("The average number is {0}.", averageNum);
}//dart
linq89(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var averageNum = avg(numbers);
print("The average number is $averageNum.");
}Output
The average number is 4.5.
linq90: Average - Projection
//c#
public void Linq90()
{
string[] words = { "cherry", "apple", "blueberry" };
double averageLength = words.Average(w => w.Length);
Console.WriteLine("The average word length is {0} characters.", averageLength);
}//dart
linq90(){
var words = [ "cherry", "apple", "blueberry" ];
var averageLength = avg(words.map((w) => w.length));
print("The average word length is $averageLength characters.");
}Output
The average word length is 6.666666666666667 characters.
linq91: Average - Grouped
//c#
public void Linq91()
{
List<Product> products = GetProductList();
var categories =
from p in products
group p by p.Category into g
select new { Category = g.Key, AveragePrice = g.Average(p => p.UnitPrice) };
ObjectDumper.Write(categories);
}//dart
linq91(){
var products = productsList();
var categories = group(products, by:(p) => p.category)
.map((g) => { 'Category': g.key, 'AveragePrice': avg(g.values.map((p) => p.unitPrice)) });
categories.forEach(print);
}Output
{Category: Dairy Products, AveragePrice: 28.73}
{Category: Grains/Cereals, AveragePrice: 20.25}
{Category: Confections, AveragePrice: 25.16}
{Category: Seafood, AveragePrice: 20.6825}
{Category: Condiments, AveragePrice: 23.0625}
{Category: Meat/Poultry, AveragePrice: 54.00666666666667}
{Category: Produce, AveragePrice: 32.37}
{Category: Beverages, AveragePrice: 37.979166666666664}
linq92: Aggregate - Simple
//c#
public void Linq92()
{
double[] doubles = { 1.7, 2.3, 1.9, 4.1, 2.9 };
double product = doubles.Aggregate((runningProduct, nextFactor) => runningProduct * nextFactor);
Console.WriteLine("Total product of all numbers: {0}", product);
}//dart
linq92(){
var doubles = [ 1.7, 2.3, 1.9, 4.1, 2.9 ];
var product = doubles.reduce((runningProduct, nextFactor) => runningProduct * nextFactor);
print("Total product of all numbers: $product");
}Output
Total product of all numbers: 88.33080999999999
linq93: Aggregate - Seed
//c#
public void Linq93()
{
double startBalance = 100.0;
int[] attemptedWithdrawals = { 20, 10, 40, 50, 10, 70, 30 };
double endBalance =
attemptedWithdrawals.Aggregate(startBalance,
(balance, nextWithdrawal) =>
((nextWithdrawal <= balance) ? (balance - nextWithdrawal) : balance));
Console.WriteLine("Ending balance: {0}", endBalance);
}//dart
linq93(){
var startBalance = 100.0;
var attemptedWithdrawals = [ 20, 10, 40, 50, 10, 70, 30 ];
var endBalance = attemptedWithdrawals.fold(startBalance,
(balance, nextWithdrawal) =>
((nextWithdrawal <= balance) ? (balance - nextWithdrawal) : balance));
print("Ending balance: $endBalance");
}Output
Ending balance: 20.0
LINQ - Miscellaneous Operators
Dart utils added
concat(Iterable seq, Iterable withSeq) =>
seq.toList()..addAll(withSeq);
bool seqEq(Iterable seq, Iterable withSeq) =>
seq.length == withSeq.length
&& range(seq.length).every((i) => seq.elementAt(i) == withSeq.elementAt(i));linq94: Concat - 1
//c#
public void Linq94()
{
int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
int[] numbersB = { 1, 3, 5, 7, 8 };
var allNumbers = numbersA.Concat(numbersB);
Console.WriteLine("All numbers from both arrays:");
foreach (var n in allNumbers)
{
Console.WriteLine(n);
}
}//dart
linq94(){
var numbersA = [ 0, 2, 4, 5, 6, 8, 9 ];
var numbersB = [ 1, 3, 5, 7, 8 ];
var allNumbers = concat(numbersA, numbersB);
print("All numbers from both arrays:");
allNumbers.forEach(print);
}Output
All numbers from both arrays:
0
2
4
5
6
8
9
1
3
5
7
8
linq95: Concat - 2
//c#
public void Linq95()
{
List<Customer> customers = GetCustomerList();
List<Product> products = GetProductList();
var customerNames =
from c in customers
select c.CompanyName;
var productNames =
from p in products
select p.ProductName;
var allNames = customerNames.Concat(productNames);
Console.WriteLine("Customer and product names:");
foreach (var n in allNames)
{
Console.WriteLine(n);
}
}//dart
linq95(){
var customers = customersList();
var products = productsList();
var customerNames = customers
.map((c) => c.companyName);
var productNames = products
.map((p) => p.productName);
var allNames = concat(customerNames, productNames);
print("Customer and product names:");
allNames.forEach(print);
}Output
Customer and product names:
Alfreds Futterkiste
Ana Trujillo Emparedados y helados
Antonio Moreno Taquer�a
Around the Horn
Berglunds snabbk�p
Blauer See Delikatessen
...
linq96: EqualAll - 1
//c#
public void Linq96()
{
var wordsA = new string[] { "cherry", "apple", "blueberry" };
var wordsB = new string[] { "cherry", "apple", "blueberry" };
bool match = wordsA.SequenceEqual(wordsB);
Console.WriteLine("The sequences match: {0}", match);
}//dart
linq96(){
var wordsA = [ "cherry", "apple", "blueberry" ];
var wordsB = [ "cherry", "apple", "blueberry" ];
bool match = seqEq(wordsA, wordsB);
print("The sequences match: $match");
}Output
The sequences match: true
linq97: EqualAll - 2
//c#
public void Linq97()
{
var wordsA = new string[] { "cherry", "apple", "blueberry" };
var wordsB = new string[] { "apple", "blueberry", "cherry" };
bool match = wordsA.SequenceEqual(wordsB);
Console.WriteLine("The sequences match: {0}", match);
}//dart
linq97(){
var wordsA = [ "cherry", "apple", "blueberry" ];
var wordsB = [ "apple", "blueberry", "cherry" ];
bool match = seqEq(wordsA, wordsB);
print("The sequences match: $match");
}Output
The sequences match: false
LINQ - Query Execution
linq99: Deferred Execution
//c#
public void Linq99()
{
// Sequence operators form first-class queries that
// are not executed until you enumerate over them.
int[] numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
int i = 0;
var q =
from n in numbers
select ++i;
// Note, the local variable 'i' is not incremented
// until each element is evaluated (as a side-effect):
foreach (var v in q)
{
Console.WriteLine("v = {0}, i = {1}", v, i);
}
}//dart
linq99(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var i = 0;
var q = numbers.map((n) => ++i);
q.forEach((v) =>
print("v = $v, i = $i"));
}Output
v = 1, i = 1
v = 2, i = 2
v = 3, i = 3
v = 4, i = 4
v = 5, i = 5
v = 6, i = 6
v = 7, i = 7
v = 8, i = 8
v = 9, i = 9
v = 10, i = 10
linq100: Immediate Execution
//c#
public void Linq100()
{
// Methods like ToList() cause the query to be
// executed immediately, caching the results.
int[] numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
int i = 0;
var q = (
from n in numbers
select ++i)
.ToList();
// The local variable i has already been fully
// incremented before we iterate the results:
foreach (var v in q)
{
Console.WriteLine("v = {0}, i = {1}", v, i);
}
} //dart
linq100(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var i = 0;
var q = numbers.map((n) => ++i).toList();
q.forEach((v) =>
print("v = $v, i = $i"));
}Output
v = 1, i = 10
v = 2, i = 10
v = 3, i = 10
v = 4, i = 10
v = 5, i = 10
v = 6, i = 10
v = 7, i = 10
v = 8, i = 10
v = 9, i = 10
v = 10, i = 10
linq101: Query Reuse
//c#
public void Linq101()
{
// Deferred execution lets us define a query once
// and then reuse it later after data changes.
int[] numbers = new int[] { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var lowNumbers =
from n in numbers
where n <= 3
select n;
Console.WriteLine("First run numbers <= 3:");
foreach (int n in lowNumbers)
{
Console.WriteLine(n);
}
for (int i = 0; i < 10; i++)
{
numbers[i] = -numbers[i];
}
// During this second run, the same query object,
// lowNumbers, will be iterating over the new state
// of numbers[], producing different results:
Console.WriteLine("Second run numbers <= 3:");
foreach (int n in lowNumbers)
{
Console.WriteLine(n);
}
} //dart
linq101(){
var numbers = [ 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 ];
var lowNumbers = numbers
.where((n) => n <= 3);
print("First run numbers <= 3:");
lowNumbers.forEach(print);
for (int i = 0; i < 10; i++){
numbers[i] = -numbers[i];
}
print("Second run numbers <= 3:");
lowNumbers.forEach(print);
}Output
First run numbers <= 3:
1
3
2
0
Second run numbers <= 3:
-5
-4
-1
-3
-9
-8
-6
-7
-2
0
LINQ - Join Operators
Dart utils added
join(Iterable seq, Iterable withSeq, bool match(x,y)) =>
seq.expand((x) => withSeq
.where((y) => match(x,y))
.map((y) => [x,y]));
joinGroup(Iterable seq, Iterable withSeq, bool match(x,y)) =>
group(join(seq, withSeq, match), by:(j) => j[0]); linq102: Cross Join
//c#
public void Linq102()
{
string[] categories = new string[]{
"Beverages",
"Condiments",
"Vegetables",
"Dairy Products",
"Seafood" };
List<Product> products = GetProductList();
var q =
from c in categories
join p in products on c equals p.Category
select new { Category = c, p.ProductName };
foreach (var v in q)
{
Console.WriteLine(v.ProductName + ": " + v.Category);
}
}//dart
linq102(){
var categories = [ "Beverages", "Condiments", "Vegetables", "Dairy Products", "Seafood" ];
var products = productsList();
var q = join(categories, products, (c,p) => c == p.category)
.map((j) => { 'Category': j[0], 'ProductName': j[1].productName });
q.forEach(print);
}Output
{Category: Beverages, ProductName: Chai}
{Category: Beverages, ProductName: Chang}
{Category: Beverages, ProductName: Guaran� Fant�stica}
{Category: Beverages, ProductName: Sasquatch Ale}
{Category: Beverages, ProductName: Steeleye Stout}
{Category: Beverages, ProductName: C�te de Blaye}
{Category: Beverages, ProductName: Chartreuse verte}
{Category: Beverages, ProductName: Ipoh Coffee}
...
linq103: Group Join
//c#
public void Linq103()
{
string[] categories = new string[]{
"Beverages",
"Condiments",
"Vegetables",
"Dairy Products",
"Seafood" };
List<Product> products = GetProductList();
var q =
from c in categories
join p in products on c equals p.Category into ps
select new { Category = c, Products = ps };
foreach (var v in q)
{
Console.WriteLine(v.Category + ":");
foreach (var p in v.Products)
{
Console.WriteLine(" " + p.ProductName);
}
}
}//dart
linq103(){
var categories = [ "Beverages", "Condiments", "Vegetables", "Dairy Products", "Seafood" ];
var products = productsList();
var q = joinGroup(categories, products, (c,p) => c == p.category)
.map((j) => { 'Category': j.key, 'Products': j.values.map((g) => g[1]) });
q.forEach((v){
print("${v['Category']}:");
v['Products'].forEach((p) => print(" ${p.productName}"));
});
}Output
Dairy Products:
Queso Cabrales
Queso Manchego La Pastora
Gorgonzola Telino
Mascarpone Fabioli
Geitost
Raclette Courdavault
Camembert Pierrot
Gudbrandsdalsost
Flotemysost
Mozzarella di Giovanni
Condiments:
Aniseed Syrup
Chef Anton's Cajun Seasoning
Chef Anton's Gumbo Mix
Grandma's Boysenberry Spread
Northwoods Cranberry Sauce
Genen Shouyu
Gula Malacca
Sirop d'�rable
Vegie-spread
Louisiana Fiery Hot Pepper Sauce
Louisiana Hot Spiced Okra
Original Frankfurter gr�ne So�e
...
linq104: Cross Join with Group Join
//c#
public void Linq104()
{
string[] categories = new string[]{
"Beverages",
"Condiments",
"Vegetables",
"Dairy Products",
"Seafood" };
List<Product> products = GetProductList();
var q =
from c in categories
join p in products on c equals p.Category into ps
from p in ps
select new { Category = c, p.ProductName };
foreach (var v in q)
{
Console.WriteLine(v.ProductName + ": " + v.Category);
}
}//dart
linq104(){
var categories = [ "Beverages", "Condiments", "Vegetables", "Dairy Products", "Seafood" ];
var products = productsList();
var q = joinGroup(categories, products, (c,p) => c == p.category)
.expand((j) => j.values.map((g) => g[1])
.map((p) => { 'Category': j.key, 'ProductName': p.productName }));
q.forEach((v) =>
print("${v['ProductName']}: ${v['Category']}"));
}Output
Queso Cabrales: Dairy Products
Queso Manchego La Pastora: Dairy Products
Gorgonzola Telino: Dairy Products
Mascarpone Fabioli: Dairy Products
Geitost: Dairy Products
Raclette Courdavault: Dairy Products
Camembert Pierrot: Dairy Products
Gudbrandsdalsost: Dairy Products
Flotemysost: Dairy Products
Mozzarella di Giovanni: Dairy Products
Aniseed Syrup: Condiments
Chef Anton's Cajun Seasoning: Condiments
Chef Anton's Gumbo Mix: Condiments
...
linq105: Left Outer Join
//c#
public void Linq105()
{
string[] categories = new string[]{
"Beverages",
"Condiments",
"Vegetables",
"Dairy Products",
"Seafood" };
List<Product> products = GetProductList();
var q =
from c in categories
join p in products on c equals p.Category into ps
from p in ps.DefaultIfEmpty()
select new { Category = c, ProductName = p == null ? "(No products)" : p.ProductName };
foreach (var v in q)
{
Console.WriteLine(v.ProductName + ": " + v.Category);
}
}//dart
linq105(){
var categories = [ "Beverages", "Condiments", "Vegetables", "Dairy Products", "Seafood" ];
var products = productsList();
var q = categories
.expand((c){
var catProducts = products.where((p) => c == p.category);
return catProducts.isEmpty
? [{ 'Category': c, 'ProductName': "(No products)" }]
: catProducts.map((p) => { 'Category': c, 'ProductName': p.productName });
});
q.forEach((v) =>
print("${v['ProductName']}: ${v['Category']}"));
}Output
Chai: Beverages
Chang: Beverages
Guaran� Fant�stica: Beverages
Sasquatch Ale: Beverages
Steeleye Stout: Beverages
C�te de Blaye: Beverages
Chartreuse verte: Beverages
Ipoh Coffee: Beverages
Laughing Lumberjack Lager: Beverages
Outback Lager: Beverages
Rh�nbr�u Klosterbier: Beverages
Lakkalik��ri: Beverages
Aniseed Syrup: Condiments
Chef Anton's Cajun Seasoning: Condiments
Chef Anton's Gumbo Mix: Condiments
Grandma's Boysenberry Spread: Condiments
Northwoods Cranberry Sauce: Condiments
Genen Shouyu: Condiments
Gula Malacca: Condiments
Sirop d'�rable: Condiments
Vegie-spread: Condiments
Louisiana Fiery Hot Pepper Sauce: Condiments
Louisiana Hot Spiced Okra: Condiments
Original Frankfurter gr�ne So�e: Condiments
(No products): Vegetables
...
Contributors
- mythz (Demis Bellot)