Protocol buffers in C# projects using protobuf-net - best practices for code generation

Question

I'm trying to use protobuf in a C# project, using protobuf-net, and am wondering what is the best way to organise this into a Visual Studio project structure.

When manually using the protogen tool to generate code into C#, life seems easy but it doesn't feel right.

I'd like the .proto file to be considered to be the primary source-code file, generating C# files as a by-product, but before the C# compiler gets involved.

The options seem to be:

1. Custom tool for proto tools (although I can't see where to start there)
2. Pre-build step (calling protogen or a batch-file which does that)

I have struggled with 2) above as it keeps giving me "The system cannot find the file specified" unless I use absolute paths (and I don't like forcing projects to be explicitly located).

Is there a convention (yet) for this?

---

Edit: Based upon @jon's comments, I retried the pre-build step method and used this (protogen's location hardcoded for now), using Google's address-book example:

c:\bin\protobuf\protogen "-i:$(ProjectDir)AddressBook.proto" 
       "-o:$(ProjectDir)AddressBook.cs" -t:c:\bin\protobuf\csharp.xslt

---

Edit2: Taking @jon's recommendation to minimise build-time by not processing the .proto files if they haven't changed, I've knocked together a basic tool to check for me (this could probably be expanded to a full Custom-Build tool):

using System;
using System.Diagnostics;
using System.IO;

namespace PreBuildChecker
{
    public class Checker
    {
        static int Main(string[] args)
        {
            try
            {
                Check(args);
                return 0;
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
                return 1;
            }
        }

        public static void Check(string[] args)
        {
            if (args.Length < 3)
            {
                throw new ArgumentException(
                    "Command line must be supplied with source, target and command-line [plus options]");
            }

            string source = args[0];
            string target = args[1];
            string executable = args[2];
            string arguments = args.Length > 3 ? GetCommandLine(args) : null;

            FileInfo targetFileInfo = new FileInfo(target);
            FileInfo sourceFileInfo = new FileInfo(source);
            if (!sourceFileInfo.Exists) 
            {
                throw new ArgumentException(string.Format(
                    "Source file {0} not found", source));
            }

            if (!targetFileInfo.Exists || 
                sourceFileInfo.LastWriteTimeUtc > targetFileInfo.LastAccessTimeUtc)
            {
                Process process = new Process();
                process.StartInfo.FileName = executable;
                process.StartInfo.Arguments = arguments;
                process.StartInfo.ErrorDialog = true;

                Console.WriteLine(string.Format(
                     "Source newer than target, launching tool: {0} {1}",
                     executable,
                     arguments));
                process.Start();
            }
        }

        private static string GetCommandLine(string[] args)
        {
            string[] arguments = new string[args.Length - 3];
            Array.Copy(args, 3, arguments, 0, arguments.Length);
            return String.Join(" ", arguments);
        }
    }
}

My pre-build command is now (all on one line):

$(SolutionDir)PreBuildChecker\$(OutDir)PreBuildChecker 
    $(ProjectDir)AddressBook.proto 
    $(ProjectDir)AddressBook.cs 
    c:\bin\protobuf\protogen 
      "-i:$(ProjectDir)AddressBook.proto" 
      "-o:$(ProjectDir)AddressBook.cs" 
      -t:c:\bin\protobuf\csharp.xslt

Answer 1

As an extension of Shaun's code, I am pleased to announce that protobuf-net now has Visual Studio integration by way of a Custom Tool. The msi installer is available from the project page. More complete information here: protobuf-net; now with added Orcas.