Let’s look at the signatures for constructors of ArgumentNullException and ArgumentException:

public ArgumentException(
	string message,
	string paramName
)

public ArgumentNullException(
	string paramName,
	string message
)

Notice how they both take two string parameters, but each has opposite order. This drives me bonkers and I can never get the right one. I kind of wish MS would make a breaking change and fix it one way or the other.