title: Protobuf-net with oneof in .proto file
body: <p>I am using the ProtoGen tool (version 1.0.0.280) from protobuf-net to generate a <code>.cs</code> file from a <code>.proto</code> file.</p>
  
  <p>However, using the <code>oneof</code> keyword results in the error:</p>
  
  <pre><code>test.proto:13:3: Expected "required", "optional", or "repeated".
  test.proto:13:25: Missing field number.
  </code></pre>
  
  <p><a href="https://stackoverflow.com/questions/18358233/how-to-generate-struct-with-protogen-from-proto-file">This question</a> mentions that <code>oneof</code> is a new feature and may not be universally supported.</p>
  
  <p>I think I have the latest ProtoGen version, but is there a newer (beta?) version which supports this functionality, or is one planned?</p>