Question

Say I have an extension method on String ShowDialog, that displays a mesagebox with the specified string.

Why I cant do now

"Hello World".ShowDialog()

and need to play with

Call "Hello World".ShowDialog()

or

CStr("Hello World").ShowDialog()

or even

Dim myString = "Hello World"
myString.ShowDialog()

or even

If "Hello World".ShowDialog() = Windows.Forms.DialogResult.OK Then
    CStr("Thank You!").ShowDialog()
End If

Answer 1

In VB.Net, expressions have to start with an identifier.

"Hello World".ShowDialog()

does not start with an identifier, hence you have to use the Call statement:

You typically use the Call keyword when the called expression doesn’t start with an identifier. Use of the Call keyword for other uses isn’t recommended.