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

Your issue is most likely synchronization. When a Dictionary is added to it sometimes needs to increase the size of the underlying structure (an array). If you are adding from multiple threads that may result in an IndexOutOfRangeException. You need to use locks etc. to make sure you are adding in a safe way.

Alternatively you can use a ConcurrentDictionary which is a thread-safe collection.