Installation

You can add a package reference with the .NET SDK:

$ dotnet add package wasmtime

Introduction

For this introduction, we'll be using a simple WebAssembly module that imports a hello function and exports a run function:

(module
  (func $hello (import "" "hello"))
  (func (export "run") (call $hello))
)

To use this module from .NET, create a new console project:

$ mkdir wasmintro
$ cd wasmintro
$ dotnet new console

Next, add a reference to the Wasmtime package:

$ dotnet add package wasmtime

Replace the contents of Program.cs with the following code:

using System;
using Wasmtime;

using var engine = new Engine();

using var module = Module.FromText(
    engine,
    "hello",
    "(module (func $hello (import \"\" \"hello\")) (func (export \"run\") (call $hello)))"
);

using var linker = new Linker(engine);
using var store = new Store(engine);

linker.Define(
    "",
    "hello",
    Function.FromCallback(store, () => Console.WriteLine("Hello from C#!"))
);

var instance = linker.Instantiate(store, module);
var run = instance.GetAction("run")!;
run();

An Engine is created and then a WebAssembly module is loaded from a string in WebAssembly text format.

A Linker defines a function called hello that simply prints a hello message.

The module is instantiated and the instance's run export is invoked.

To run the application, simply use dotnet:

$ dotnet run

This should print Hello from C#!.

Contributing

Building

Use dotnet to build the repository:

$ dotnet build Wasmtime.sln

This will download the latest development snapshot of Wasmtime for your platform.

Testing

Use dotnet to run the unit tests:

$ dotnet test Wasmtime.sln

Creating the NuGet package

Use dotnet to create a NuGet package:

$ cd src
$ dotnet pack Wasmtime.sln -c Release /p:Packing=true

This will create a .nupkg file in src/bin/Release.

By default, local builds will use a -dev suffix for the package to differentiate between official packages and development packages.