We had a little debate internally on the correct spelling for “can not” in exception message strings. One of the testers actually dug up a series of bugs where we changed one message back and forth several times. Well, I am happy to say that we have the official word on this. The UE manager for the .NET Framework weighted in with a definitive decree. We have decided to use “cannot”.
If this was a matter of needless debate on your team please feel free to put it to rest now and consider “cannot” the correct spelling.