I’m afraid that you are confused.
arrayA is declared to have type
double then it is impossible for
arrayA to be
The type of
null is not a member of that type. Not ever. The
null value is only valid for reference types, and
double is a primitive type, not a reference type.
Either the program is not as you are describing it, or something else is causing a different value to be placed into the text box.
arrayA was declared to be a
Double, it would be a different matter.)