Here is my code:

            var dict = new Dictionary<string, int>();
            dict["1"] = 1;
            var toDelete = dict.Where(x => true);
            foreach (var kvpair in toDelete)
            {
                dict.Remove(kvpair.Key);
            }            

I don't see how I'm modifyingtoDelete in my foreach loop...Can anyone explain why this is happening?

Thanks,
-Vivek.

If i use toDelete.ToArray() for the enumeration, no exception is thrown.
I guess whatever default representation Where() was returning stores back pointers and messes with the original container.