Provide (safe) access to reflection protos in C#

[jskeet]

What language does this apply to?

C#

Describe the problem you are trying to solve.

Some APIs (e.g. BigQuery Storage use DescriptorProto for schema descriptions.

In C# we have access to reflection via the MessageDescriptor type, but there's no access to the underlying proto.

Describe the solution you'd like

ToProto() methods in all descriptor types, returning a clone of the underlying proto.

Describe alternatives you've considered

Access via .NET reflection :(

Additional context

I'll create a PR to implement this.

[jtattermusch]

Makes sense. I think historically we had to hide the *DescriptorProto values since protobuf C# didn't have support for proto2 and the descriptor messages are proto2 messages. Not that we had proto2 support for a while, I guess we can provide access to the descriptor messages (if done in a safe way).

[jskeet]

I think historically we had to hide the *DescriptorProto values since protobuf C# didn't have support for proto2 and the descriptor messages are proto2 messages.

Yes, absolutely.