>>The answer is in the sample
>>
>>If TryGetValue() returns true, it was in
>>
>>There's also ContainsKey() - but TryGetValue() tells you whether the image was in and if it was returns the data via the out parameter
>>
>>http://msdn.microsoft.com/en-us/library/xfhwa508(v=vs.110).aspx
>
>Thanks, so you would recommand TryGetValue() instead of ContainsKey(). Is that correct?

If you need the data, use TryGetValue(). If you only need to know if it exists, use ContainsKey().