Why does .ToString() on a null string cause a null error, when .ToString() works fine on a nullable int with null value?

Question

selectedItem has two fields:

• int? _cost
• string _serialNumber

In this example, _cost

Answer 1

what i think the reason is, when the compiler encounters a primitive data type it wraps it, to its corresponding object. The toString() method call is just an indirect call(wrapping and then calling the method) here and the exception is handled there. While in the case of String, we are directly calling the method. When pointing to a null, the method throws the exception.