How to Test C# Functions interactively with F# Interactive

Question

I have a set of static utility methods including unit tests. But I'd like to have a more interactive way to employ a testing -> fixing -> compiling cycle (REPL) like in Lisp or Smalltalk where one can immediately execute code in interactive mode. I tried to use F# Interactive to test these methods directly from within the opened C# project in VS 2010, but I didn't get it to work.

I know that I have to load the assembly (#r directive), open the namespace and then can call the methods (and inspect the result). But how do I do it within “F# Interactive” in Visual Studio 2010? I know it is possible with the “Immediate” window available in debug mode, but I want to do it within F# Interactive in "design mode", when I'm writing the code.

Answer 1

You need to include the path to your project using the #I directive then you may load your assembly and use it. I wrote a simple C# console app try this and got this to work.

using System;

namespace ConsoleApplication1
{
    public class Program
    {
        static void Main(string[] args)
        {
            PrintMessage();
            Console.Write("Press any key to continue . . . ");
            Console.ReadKey(true);
            Console.WriteLine();
        }

        public static void PrintMessage()
        {
            Console.WriteLine("MESSAGE!");
        }
    }
}

Then in F# interactive:

> #I "full path to debug directory";;

--> Added 'full path to debug directory' to library include path

> #r "ConsoleApplication1.exe";;

--> Referenced 'full path to debug directory\ConsoleApplication1.exe'

> open ConsoleApplication1;;
> Program.PrintMessage();;
MESSAGE!
val it : unit = ()

So it definitely works, you just need to compile your projects first. Just remember to reset your session to release your assembly beforehand.