C# oneoof help

[David Vescovi]

First I tried this simple protobuf with compiler 3.3:

syntax = "proto3";

message ProxyMessage {

int32 Signal = 1;

oneof payload

 {

  repeated int32 a= 6;

  repeated float b = 7;

  }

}

while this seem quite simple it resulted in the following error:

protoc --csharp_out=. proxy.proto
proxy.proto:7:7: Fields in oneofs must not have labels (required / optional / repeated).
proxy.proto:8:7: Fields in oneofs must not have labels (required / optional / repeated).

Is there a workaround? Is this a known bug?

I know you can, in effect,  do this same thing in proto3 by not using the oneof and rely on "optional by default" feature.

The reason I need the oneof is the fact on the other end I am using C++ and I need the oneof union feature to keep the buffer allocation down.

That being said I really need something like:

syntax = "proto3";

　

message A

{

   repeated int32 Int32Parameters = 1;

}

message B

{

   repeated float FloatParameters = 1;

}

　

message ProxyMessage {

int32 Signal = 1;

oneof payload

  {

  A a= 6;

  B b = 7;

  }

}

This actually compiles but when I try to construct a message by doing something like this:

public MainPage()

{

  this.InitializeComponent();

  RepeatedField<int> myInts = new RepeatedField<int>();

  myInts.Add(2);

  myInts.Add(3);

  ProxyMessage proxy = new ProxyMessage();

  proxy.Signal = 5;

  proxy.A.Int32Parameters.AddRange(myInts);

}

I get a NullReferenceException when it hits the AddRange line.

I also tried adding the line:

proxy.PayloadCase = ProxyMessage.PayloadOneofCase.A;

but this will not compile with "..can not assigned to --it is read only"

any ideas?

Dave

[Marc Gravell]

the language guide is very clear and explicit that this is intentional; it is nothing to do with the C# part, and will behave the same for any language:

> You can add fields of any type, but cannot use the required, optional, or repeated keywords.

https://developers.google.com/protocol-buffers/docs/proto#oneof

And:

> A oneof cannot be repeated.

https://developers.google.com/protocol-buffers/docs/proto3#oneof

So: no, you can't do what you want here. Maybe use encapsulation. So: have a message that *contains* a repeated field, and use that message type in the one-of.

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[David Vescovi]

simple resolution to the second issue ...forgot the proxy.A = new A();

oops.