Where can I submit request for new features in the C# language?

GitHub Issues:

• C# language
• VB language
• C# cross cutting VB
• Roslyn discussions on the Rosyln compiler (only)
• CoreFX This includes things like System.Collections, System.IO for .NET Core (.NET Core 2.0)
• CoreCLR This covers RyuJIT, GC and mscorlib for .NET Core (.NET Core 2.0)
• ASP.NET Core This is for ASP.NET Core (.NET Core 2.0)
• ASP.NET 4.7 - unknown

Historical places not for current discussion:

• Roslyn C# Language Design forum
• Roslyn discussions on C# 6.0, C# 7.0 and beyond

There is also the Visual Studio Uservoice for requests pertaining to Visual Studio specifically

GitHub is the correct place to lodge these requests. Raise them as GitHub issues.

https://github.com/dotnet/csharplang

https://connect.microsoft.com/

Update: Connect has been retired. This GitHub repo is now the place to add suggestions.