What happens to C# Dictionary lookup if the key does not exist?

Question

I tried checking for null but the compiler warns that this condition will never occur. What should I be looking for?

Answer 1

The Dictionary throws a KeyNotFound exception in the event that the dictionary does not contain your key.

As suggested, ContainsKey is the appropriate precaution. TryGetValue is also effective.

This allows the dictionary to store a value of null more effectively. Without it behaving this way, checking for a null result from the [] operator would indicate either a null value OR the non-existance of the input key which is no good.