Question

I have a function that accepts a String by reference:

Function Foo(ByRef input As String)

If I call it like this:

Foo(Nothing)

I want it to do something different than if I call it like this:

Dim myString As String = Nothing
Foo(myString)

Is it possible to detect this difference in the way the method is called in VB .NET?

Edit

To clarify why the heck I would want to do this, I have two methods:

Function Foo()
  Foo(Nothing)
End Function

Function Foo(ByRef input As String)
  'wicked awesome logic here,  hopefully
End Function

All the logic is in the second overload, but I want to perform a different branch of logic if Nothing was passed into the function than if a variable containing Nothing was passed in.

Answer 1

No. In either case, the method “sees” a reference to a string (input) which is pointing to nothing.

From the method’s point of view, these are identical.