Question

I am trying to delete all the items in my Hashtable with this code

Monitor.Enter(myhasatable);
 foreach (object key in myhasatable.Keys)
            {

                    myhasatable.Remove(key.ToString());

            }
 Monitor.Exit(myhasatable);

I am getting error :

system.invalidoperationexception collection was modified enumeration
operation may not execute

and them my server get stuck until I refresh it

Any idea what can cause this problem?

Thnaks

Answer 1

You can’t modify a collection while you iterate over it. Try calling Clear instead.

Also, try to avoid using Hashtable in new code. Prefer to use Dictionary<TKey, TValue> if you have a choice.

Your server deadlocks because the Monitor.Exit is not reached when an exception is thrown on the line before. You could fix this by putting that code in a finally block. But instead of using a Monitor, I suggest you use lock as this automatically releases the lock for you even in the presence of exceptions.

With all these changes, your code becomes much simpler:

lock (dict)
{
    dict.Clear();
}