Question

In my windows form application, I’m trying to test the user’s ability to access a remote machine’s shared folder. The way I’m doing this (and I’m sure that there are better ways…but I don’t know of them) is to check for the existence of a specific directory on the remote machine (I’m doing this because of firewall/other security restrictions that I’m confronted with in my organization). If the user has rights to access the shared folder, then it returns in no time at all, but if they don’t, it hangs forever. To solve this, I threw the check into another thread and wait only 1000 milliseconds before determining that the share can’t be hit by the user. However, when I do this, it still hangs as if it was never run in the same thread.

What is making it hang and how do I fix it? I would think that the fact that it is in a separate thread would allow me to just let the thread finish on it’s own in the background.

Here is my code:

bool canHitPath = false;
Thread thread = new Thread(new ThreadStart(() =>
{
    canHitPath = Directory.Exists(compInfo.Path);
}));
thread.Start();
thread.Join(1000);

if (canHitPath == false)
{
    throw new Exception("Cannot hit folder: " + compInfo.Path);
}

Edit: I feel that I should add that the line of throwing the exception IS HIT. I’ve debugged this and verified it…however, when the exception is thrown, then is when my program hangs. (I might also add that the exception is caught in the calling method and I never get to the catch statement in the debugger.)

Answer 1

I found the real problem:

The property compInfo.Path is doing a check for a directory existence on the remote file system to determine if the remote machine is 64 bit or not. Depending on the results, it returns a different value. I tried commenting out the the check and it executed successfully. This explains why I couldn’t get past the throwing of the exception, I call compInfo.Path in the message of the exception.

However, I think we learned a lot from “the real problem”:

1. The code I posted in the question (as is) works perfectly fine.
2. thread.Join(int) will exit after the specified time interval regardless of the fact that the thread may still be executing code.
3. The thread being joined CAN be running an IO operation (thus tying up a file/directory) and the desired result will still come about when doing a thread.Join(int).
4. Using the “step into” button on a debugger will reveal many things…even about your own “solid” code. 🙂

Thanks everyone for your help, patience, and thoughtful input/insights.