[EDIT: Nov. 12, 2012 I've updated the editor to fix a bug in the editor and include the source code]

For impatient 3ds Max developers the ability to compile and run C# programs from within 3ds Max without having to restart it can be very useful. Since I am about as impatient as they come I developed a simple plug-in for 3ds Max that allows me to edit and run C# programs as if they were scripts.

You can download the C# script editor plug-in and source code here. To install it copy the plug-in DLL file (and optionaly the PDB debug database) into the "binassemblies" sub-folder of your 3ds Max 2013 installation.  This should work on both 32-bit and 64-bit flavors of 3ds Max.

Next you will have to "unblock" the DLL (at least for Windows 7, I'm not sure if it is required for Vista). Right click on the file in Windows Explorer after copying it to the "binassemblies" folder and press the unblock window.

When you restart 3ds Max, you will have a new user action in the category ".NET Plug-ins" that you will need to associate with a shortcut key or menu item. The plug-in should work for both 32-bits and 64-bit flavors of 3ds Max, but won't work on 3ds Max 2012 or earlier.

I've also included a sample program called "DemoScript_BentCylinder.cs" that you should be able to run from the editor.

Implementation Details

The following code compiles the source code of one or more files each passed as a string.

/// Looks for and executes a public static function named Main by searching all types in the assembly.
/// If more than one Main function is found or no Main function is found an exception is thrown. 
public static void RunMain(Assembly asm, params string[] args)
{
    MethodInfo main = null;
    foreach (var t in asm.GetTypes())
        foreach (var mi in t.GetMethods(BindingFlags.Public | BindingFlags.Static))
            if (mi.Name == "Main")
                if (main != null)
                    throw new Exception("Multiple Main methods found");
                else 
                    main = mi;
    if (main == null)
        throw new Exception("No static public Main method found in assembly");
    main.Invoke(null, new object[] { args });
}

/// Compiles source code given the language provider (e.g. CSharpCodeProvider or VBCodeProvider). 
/// The named assemblies are referenced. The contents of each source code file is passed as a 
/// separate "input" string.  Returns the generated assembly if successful or a list of errors. 
public static CompilerResults Compile(CodeDomProvider provider, IEnumerable<string> assemblies, params string[] input) 
{ 
    var param = new System.CodeDom.Compiler.CompilerParameters(); 
    param.GenerateInMemory = true; 
    foreach (var asm in assemblies) 
        param.ReferencedAssemblies.Add(asm); 
    return provider.CompileAssemblyFromSource(param, input); 
} 

If compilation is successful the generated assembly is returned as part of the CompilerResults. Once you have the assembly you can invoke the Main entry point as long as it is a public static method of any public type using the following bit of reflection magic:

        public static void RunMain(Assembly asm, params string[] args)
        {
            MethodInfo main = null;
            foreach (var t in asm.GetTypes())
                foreach (var mi in t.GetMethods(BindingFlags.Public | BindingFlags.Static))
                    if (mi.Name == "Main")
                        main = mi;
            if (main == null)
                throw new Exception("No static public Main method found in assembly");
            main.Invoke(null, new object[] { args });
        }

The rest of the code in the plug-in is pretty unremarkable but. I'd love to hear if this tool (or some derivation) finds its way into your toolbox.