Question

I have a very strange problem with my code. It will fully run the 1st for loop, then complete the foreach, but then it will skip back to the “ThreadStart IMAPDelegate” (line 1 of the for loop) and then crash because of an ArgumentOutOfRangeException. Can someone explain why the program is doing this? I debugged it line by line and it literally just skips back up into the a line in the for loop. If it had normally run the for loop again, it would have set x back to 0 and it would not have crashed. Any suggestions?

for (int x = 0; x < UserInfo.Count; x++)
{
    ThreadStart IMAPDelegate = delegate{SendParams(UserInfo[x], IMAPServers[x]); };
    MyThreads.Add(new Thread(IMAPDelegate));
}

foreach (Thread thread in MyThreads)
{
    thread.Start();
}

Answer 1

This is by design when you use an anonymous method like that. As soon as the thread starts running, it executes the SendParams() method call. Which then bombs because the “x” variable is already incremented beyond UserInfo.Count. Fix:

for (int x = 0; x < UserInfo.Count; x++)
{
    int user = x;
    ThreadStart IMAPDelegate = delegate{SendParams(UserInfo[user], IMAPServers[user]); };
    MyThreads.Add(new Thread(IMAPDelegate));
}