Process.WaitForExit() doesn't actually wait for the process to completely exit?

Question

Hi,

I have a situation where I want to execute a file, and then delete the executable file when the execution is done.
I use System.Diagnostics.Process.Start() to execute the the file, and use .WaitForExit() to wait for the process to complete.
I then use File.Delete(filename) to delete the executable file.

The problem is that sometimes, File.Delete will fail with the following error:

Unhandled Exception: System.UnauthorizedAccessException: Access to the path 'c:\workspace\ss.exe' is denied.
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.File.InternalCopy(String sourceFileName, String destFileName, Boolean overwrite)
   at System.IO.File.Copy(String sourceFileName, String destFileName)
   at ConsoleApplication1.Program.Main() in C:\workspace\test\ConsoleApplication1\Program.cs:line 22

This leads me to believe that, somehow, the process is still alive and locking the executable file even after the .WaitForExit() call returns.

I have found other threads on the net that describe the same behavior, but I have not found any that conclude with a reasonable explanation or solution to the problem, other than suggestions of placing a Sleep(n) after the WaitForExit().  Examples:

http://stackoverflow.com/questions/1310791/deletefile-of-an-exe-immediately-after-process-waitforexit-fails
http://groups.google.com/group/microsoft.public.dotnet.languages.csharp/msg/4e18b2bcdae598c4

Here is a sample program that reproduces the problem for me.  I have tested on both Windows XP and Windows 7, and they both eventually fail at some point with the same error.

Also note that the ss.exe executable is a plain simple "Hello World" console application...

using System;
using System.Collections.Generic;
using System.Text;
using System.Linq;
using System.IO;
using System.Diagnostics;
using System.Threading;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            const string filenamepart = @"c:\workspace\ss";
            const string filename = filenamepart + ".exe";

            Console.WriteLine("start");

            for (int i = 0; i < 100; i++)
            {
                File.Copy(filenamepart, filename);
                Console.WriteLine(i + ". " + RunProcess(filename));
                File.Delete(filename); // will some times crash on this line...
            }

            Console.WriteLine("end");
        }

        private static int RunProcess(string filename)
        {
            ProcessStartInfo startInfo = new ProcessStartInfo(filename);
            startInfo.RedirectStandardError = true;
            startInfo.RedirectStandardOutput = true;
            startInfo.UseShellExecute = false;

            using (Process p = new Process())
            {
                p.StartInfo = startInfo;
                p.Start();

                p.WaitForExit();
                // Thread.Sleep(1000);  // adding the sleep here makes the problem go away...

                Console.Write(p.StandardOutput.ReadToEnd());
                Console.Write(p.StandardError.ReadToEnd());

                return p.ExitCode;
            }
        }
    }
}

and the output typically looks something like (with varying amount of iterations before the crash occurs):

start
hello world
0. 0
hello world
1. 0
hello world
2. 0
hello world
3. 0
hello world
4. 0
hello world
5. 0
hello world
6. 0
hello world
7. 0
hello world
8. 0
hello world
9. 0
hello world
10. 0
hello world
11. 0
hello world
12. 0
hello world
13. 0

Unhandled Exception: System.UnauthorizedAccessException: Access to the path 'c:\workspace\ss.exe' is denied.
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.File.InternalCopy(String sourceFileName, String destFileName, Boolean overwrite)
   at System.IO.File.Copy(String sourceFileName, String destFileName)
   at ConsoleApplication1.Program.Main() in C:\workspace\test\ConsoleApplication1\Program.cs:line 22
Press any key to continue . . .

Any ideas on why this happens, and if there is some fix for this (other than putting sleeps in the code)?

Thanks
Sam