https://github.com/grpc/grpc/tree/master/src/csharp - There are currently two official implementations of gRPC for C# The original gRPC C# implementation based on the native gRPC Core library (the source code lives in this directory) The new "gRPC for .NET" implementation written in pure C# and based on the newly released .NET Core 3 (source code available at https://github.com/grpc/grpc-dotnet)