Adding to a generic dictionary causes IndexOutOfRangeException

Question

I\'m using a dictionary inside of some Task.

Logically I have set it up so that my Keys will never clash, though sometimes when I am adding to the dictionary I get this

Answer 1

You should have looked to the documentation. That what it says:

A Dictionary can support multiple readers concurrently, as long as the collection is not modified. Even so, enumerating through a collection is intrinsically not a thread-safe procedure. In the rare case where an enumeration contends with write accesses, the collection must be locked during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization. For a thread-safe alternative, see ConcurrentDictionary.