There are a couple partial .NET runtimes reimplemented in JavaScript rather than compiled to WebAssembly; they are usually tied in with C# -> JavaScript generators.

https://github.com/nikhilk/scriptsharp was kind of the granddaddy of them all, with no updates since 2013.

https://github.com/bridgedotnet/Bridge Saltarelle was acquired by Bridge.NET mid-2015: https://blog.bridge.net/bridge-net-acquires-saltarelle-c77a9... and seems to be going strong.

https://github.com/SharpKit/SharpKit went the other way and is now open source, but original L/GPL/references to licensing for commercial use may have limited growth; it is now MIT.

http://jsil.org/ mostly demonstrates games, and focuses on translating MSIL bytecode rather than any specific language or runtime.