Both ArgumentNullException and ArgumentException have a constructor which takes two strings.  One is the name of the parameter (or argument) in question and the other is a string describing the exception.

The funny/odd/interesting thing about them is that one has the opposite order of arguments.

For ArgumentException the constructor is:

   1: public ArgumentException(
   2:     string message,
   3:     string paramName
   4: )


While for ArgumentNullException is it:

   1: public ArgumentNullException(
   2:     string paramName,
   3:     string message
   4: )


And my point is....

Well, I don't have one I just thought it was an interesting thing to point out :)