The Microsoft Build Engine (MSBuild) build platform for .NET and VS
OmniSharp server (HTTP, STDIO) based on Roslyn workspaces
PerfView is a CPU and memory performance-analysis tool
Cross platform code coverage for .NET
Vulnerability Patterns Detector for C# and VB.NET
Tool for building and deploying Microsoft.NET applications.
An example project to demonstrate continuous integration, in .NET.
A concurrency and load testing tool for .NET applications