C# – With NAnt, How to use C# 3.0 compiler while targetting .NET 2.0 runtime

C#3 and .Net 3.5 adds new assemblies, but the IL is unchanged.

This means that with .Net 2 assemblies you can compile and use C#3, as long as you don't use Linq or anything else that references System.Linq or System.Core

yield, var, lambda syntax, anon types and initialisers are all compiler cleverness. The IL they produce is cross-compatible.

If you can reference the new assemblies for 3.5 it should all just work.

There is no new version of ASP.Net - it should still be 2.0.50727 - but you should still compile for 3.5

I wonder if you have to change the framework that NAnt is running under.

Also, look into the NAntContrib project. That has the MSBuild task. We use this to build our 2008 projects, where we use the fancy sytax sugar like what you want, down to 2.0 assemblies. One thing we had to do though was replace the MSBuild.exe in the C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727 with one that forwards the request on to the 3.0 MSBuild.exe

Here is the code we use to replace MSBuild.exe in the 2.0 path. I can't remember where I got this code. I tried to find it online but can't.

Build this to MSBuild.exe and replace your 2.0 one with this one.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;

namespace MSBuild
{
    public class Program
    {
        public static int Main(string[] args)
        {
            for (int argIndex = 0; argIndex < args.Length; argIndex++)
            {
                if (args[argIndex].Contains(" "))
                {
                    string quotedArg = string.Format("\"{0}\"", args[argIndex]);
                    args[argIndex] = quotedArg;
                }
            }

            string arguments = string.Join(" ", args);

            // HACK: I should probably change
            //       this to automaticlaly 
            //       determine the path

            Process process = Process.Start("C:\\WINDOWS\\Microsoft.NET\\Framework\\v3.5\\MSBuild.exe",arguments);

            process.WaitForExit();

            return process.ExitCode;

        }
    }
}