Use the batch files to generate the code. For C# the nuget package Grpc.Tools must be installed. Also install the package Grpc for using the API.
For C++ use ninja & cmake as described in https://github.com/grpc/grpc/blob/master/INSTALL.md : (Use VS Developer Command Prompt)
For VS2017 replace: > call "%VS140COMNTOOLS%....\VC\vcvarsall.bat" x64 with: > call "%VS150COMNTOOLS%....\VC\Auxiliary\Build\vcvarsall.bat" x64