hi,
i have encountered a strange behaviour when using ref parameters with
delegates.  basically the changed value is not reflected back to the
original calling method.

to prove the point, run this simple console application. it sets a
string variable 's' with the current number of Ticks, then invokes a
method via a delegate, waits for it to finish, and outputs the
supposed-to-be-changed value.  the value is changed in the method, but
is not reflected back.

using System;
using System.Threading;

namespace TestRef
{
    class Class1
    {
        [STAThread]
        static void Main(string[] args)
        {
            new Class1();
        }

        public Class1()
        {
            string s = DateTime.Now.Ticks.ToString();
            Console.WriteLine("Initialised: \t\t" + s);

            // invoke a method using a delegate
            new TestByRefDelegate(this.TestByRef).BeginInvoke(ref s, null,
null);
            Thread.Sleep(500);  // wait until the other thread is finished
            Console.WriteLine("After delegate: \t" + s);

            Console.Read();
        }

        public delegate void TestByRefDelegate(ref string s);
        public void TestByRef(ref string s)
        {
            Console.WriteLine("Start of delegate: \t" + s);
            s = DateTime.Now.Ticks.ToString();
            Console.WriteLine("End of delegate: \t" + s);
        }
    }
}

can anyone shed some light on this?   i just realised that it's of
course because the value is changed on the new thread, but that is
disposed of as soon as it finishes.  this then begs the question, why
does the compiler allow delegates with ref parameters, since it is
impossible for the value to survive the lifetime of the thread?

thanks
tim