How to remove elements from a generic list while iterating over it?

Question

I am looking for a better pattern for working with a list of elements which each need processed and then depending on the outcome are removed from

Answer 1

 foreach (var item in list.ToList()) {
     list.Remove(item);
 }

If you add ".ToList()" to your list (or the results of a LINQ query), you can remove "item" directly from "list" without the dreaded "Collection was modified; enumeration operation may not execute." error. The compiler makes a copy of "list", so that you can safely do the remove on the array.

While this pattern is not super efficient, it has a natural feel and is flexible enough for almost any situation. Such as when you want to save each "item" to a DB and remove it from the list only when the DB save succeeds.