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Asked: 2026-06-01T14:52:05+00:00

My question is related with the C# implementation of the google protocol buffers (protobuf-csharp-port,

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My question is related with the C# implementation of the google protocol buffers (protobuf-csharp-port, by jon skeet, great job!)

I am experiencing troubles with the extensions: let’s say I wrote:

  • "transport_file.proto" with a "transport message" and some code to
    deal with it "code_old".
  • and I wrote an extension of the transport message on
    "Mytransport.proto" file, and new code to read it "code_new".

I’m trying to read a new message (from MyTransport.proto) with the code_old expecting to ignore the extension, but I get an exception in the merge method from TextFormat: "transport" has no field named "whatever_new_field"

Transport.Builder myAppConfigB = new Transport.Builder();
System.IO.StreamReader fich = System.IO.File.OpenText("protocolBus.App.cfg");
TextFormat.Merge(fich.ReadToEnd(),myAppConfigB);
fich.Close();

new extended file looks like:

...
  Transport 
  { 
     TransportName: "K6Server_0"
     DllImport: "protocolBus.Transports.CentralServer"
     TransportClass: "K6Server"
     K6ServerParams
     {
        K6Server { host: "85.51.11.23" port: 40069 }
        Service: "TZinTalk"
        ...
     }
  }
...

while the old one, not extended:

...
  Transport 
  { 
     TransportName: "K6Server_0"
     DllImport: "Default"
     TransportClass: "Multicast"
  }
...

The whole idea is to use the text based protocol buffer as a config file in which I write some params, and based on one of those I load and assembly (which will read the whole message with the new extension (params to initialize the object).

Any idea? (it is a desperate question 😀 )

I’m using MSVC# 2008Express edition, protobuf-csharp-port version 0.9.1 (someday I’ll upgrade everything).

THANKS in advance.

I’m working on a non centrilized Publish-Subscribe framework of messages (for any written message in a proto file I auto create a Publish and a Subscriber class) with different transports. By the default I use multicast, but broadcast and a "UDP star" are also included. I let the extension mechanism to let people add new transports with its owm config params that should be read by my main code_old (just to load the assembly) and let the new transport (.dll) read it again (fully).
Curious? the previous, almost functional, version is in http://protocolbus.casessite.org

Update 1

Extended types in text format are enclosed in brackets (good to know, I was not aware of it 😀 ) so I should have written:

 [K6ServerParams]
 {
    K6Server { host: "85.51.11.23" port: 40069 }
    Service: "TZinTalk"
    ...
 }
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1 Answer

  1. Editorial Team

    Protocol buffers are designed to be backwards and forwards compatible when using their binary format, but certainly the current code doesn’t expect to parse the text format with unknown fields. It could potentially be changed to do that, but I’d want to check with the Java code to try to retain parity with that.

    Is there any reason you’re not using the binary representation to start with? That’s the normal intended usage, and the one where the vast majority of the work has gone in. (Having said which, it all seems a bit of a blur after this long away from the code…)

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