Using CSharpCodeProvider with .net 4.5 beta

Question

I recently installed the Visual Studio 11 Beta, and I'm trying to update an existing 4.0 project to use 4.5. In the program it compiles some dynamically generated code using CSharpCodeProvider.

/// <summary>
/// Compile and return a reference to the compiled assembly
/// </summary>
private Assembly Compile()
{
    var referencedDlls = new List<string>
    {
        "mscorlib.dll",
        "System.dll",
        "System.Core.dll",
    };
    referencedDlls.AddRange(RequiredReferences);

    var parameters = new CompilerParameters(
        assemblyNames: referencedDlls.ToArray(),
        outputName: GeneratedDllFileName,
        // only include debug information if we are currently debugging
        includeDebugInformation: Debugger.IsAttached);
    parameters.TreatWarningsAsErrors = false;
    parameters.WarningLevel = 0;
    parameters.GenerateExecutable = false;
    parameters.GenerateInMemory = false;
    parameters.CompilerOptions = "/optimize+ /platform:x64";

    string[] files = Directory.GetFiles(GenerationDirectory, "*.cs");

    var compiler = new CSharpCodeProvider(
        new Dictionary<string, string> { { "CompilerVersion", "v4.5" } });
    var results = compiler.CompileAssemblyFromFile(parameters, files);

    if (results.Errors.HasErrors)
    {
        string firstError =
            string.Format("Compile error: {0}", results.Errors[0].ToString());
        throw new ApplicationException(firstError);
    }
    else
    {
        return results.CompiledAssembly;
    }
}

The problem comes when I changed the CompilerVersion from { "CompilerVersion", "v4.0" } to { "CompilerVersion", "v4.5" }

I now get an exception

Compiler executable file csc.exe cannot be found.

Is specifying CompilerVersion the wrong way to tell it to use 4.5? Will compiling it as v4.5 even make a difference since the code won't be using any new 4.5 specific features?

Answer 1

It would have helped if you'd given us a short but complete program to demonstrate the problem, but I can verify that with "v4.0" it will work and compile async methods, assuming you're running on a machine with the VS11 beta installed.

Demonstration:

using System;
using System.Collections;
using System.Reflection;
using System.Collections.Generic;
using System.Diagnostics;
using Microsoft.CSharp;
using System.CodeDom.Compiler;

namespace Foo {}

class Program
{
    static void Main(string[] args)
    {
        var referencedDll = new List<string>
        {
            "mscorlib.dll",
            "System.dll",
            "System.Core.dll",
        };

        var parameters = new CompilerParameters(
             assemblyNames: referencedDll.ToArray(),
             outputName: "foo.dll",
             includeDebugInformation: false)
        {
            TreatWarningsAsErrors = true,
            // We don't want to be warned that we have no await!
            WarningLevel = 0,
            GenerateExecutable = false,
            GenerateInMemory = true
        };

        var source = new[] { "class Test { static async void Foo() {}}" };

        var options = new Dictionary<string, string> {
             { "CompilerVersion", "v4.0" }
        };
        var compiler = new CSharpCodeProvider(options);
        var results = compiler.CompileAssemblyFromSource(parameters, source);

        Console.WriteLine("Success? {0}", !results.Errors.HasErrors);
    }
}