Elastic APM .NET Agent
App Metrics is an open-source and cross-platform .NET library used to record and report metrics within an application.
No longer maintained, instead see - https://github.com/alhardy/AppMetrics/
Powerful .NET library for benchmarking
Cross platform code coverage for .NET
[Archived] Diagnostics middleware for reporting info and handling exceptions and errors in ASP.NET Core, and diagnosing Entity Framework Core migrations errors. Project moved to https://github.com/aspnet/AspNetCore
A simple but effective mini-profiler for ASP.NET (and Core) websites
MarkPad - a visual Markdown editor (inspired by the Downmarker project)
A chaotic experimental playground for new features and ideas - check here for small and simple samples for individual features.
Exceptionless application
Gendarme is a extensible rule-based tool to find problems in .NET applications and libraries. Gendarme inspects programs and libraries that contain code in ECMA CIL format (Mono and .NET) and looks for common problems with the code, problems that compiler do not typically check or have not historically checked.
Linq to database provider.
The Metrics.NET library provides a way of instrumenting applications with custom metrics (timers, histograms, counters etc) that can be reported in various ways and can provide insights on what is happening inside a running application.
NsDepCop is a static code analysis tool that helps to enforce namespace dependency rules in C# projects. No more unplanned or unnoticed dependencies in your system.
A business logic micro-framework for .NET and .NET Core
A site generation tool (and then some) for .NET platforms
Download ScriptAnalyzer from PowerShellGallery
[Archived] Middleware for security and authorization of web apps. Project moved to https://github.com/aspnet/AspNetCore
Code analyzer for C# and VB.NET projects https://redirect.sonarsource.com/plugins/vbnet.html
#1 .NET BDD Framework. SpecFlow automates your testing & works with your existing code. Find Bugs before they happen. Behavior Driven Development helps developers, testers, and business representatives to get a better understanding of their collaboration
Cross platform HTTP server benchmark tool