Microsoft's CNTK allows you to run trained models on C# and another programming languages (https://docs.microsoft.com/en-us/cognitive-toolkit/CNTK-usage-overview).
Full train on C#:
It seems like the contributors on github are working on it, check these threads:
https://github.com/Microsoft/CNTK/issues/1967
https://github.com/Microsoft/CNTK/issues/960
There seem to be an early effort, haven't tried though: https://github.com/Lokad/cntksharp
As microsoft has a very important support to C# due to its .NET framework, I would expect to have C# bindings on CNTK soon.