How to prevent empty String in VB/ASP.Net function parameter

Question

How would I prevent other developers from enter "" or " " into the following function/sub?

Public Sub MyFunction(MyString as String)

End Sub

' Call:
MyFunction("")

I want them to end up with a non compileable app.

I don't think that the content of a string is available at compile time. — Giannis Paraskevopoulos
– Giannis Paraskevopoulos, Commented Oct 10, 2013 at 13:02
Well, I'm not talking about string variables but rather hardcoded strings, e.g. "This is going in" — Matthias Max
– Matthias Max, Commented Oct 10, 2013 at 13:04

Douglas Barbin · Accepted Answer · 2013-10-10 13:10:41Z

1

There is no way to prevent compilation based on what is passed to the string. You can, however, simply prevent the method from executing, like this:

Public Sub MyFunction(myString as String)
    If Not String.IsNullOrWhitespace(myString) Then
        ' Do stuff here
    End If 
End Sub

Your other option is to throw an exception:

Public Sub MyFunction(myString as String)
    If String.IsNullOrWhitespace(myString) Then
        Throw New ApplicationException("No empty or whitespace strings allowed!")
    Else
        ' Do stuff here
    End If 
End Sub

answered Oct 10, 2013 at 13:10

Douglas Barbin

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1 Comment

Matthias Max Over a year ago

Hi, OK, I see I can't achieve what I want. This way the end user would get the message. I don't want this. Thank you anyway!

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