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The Visual Basic runtime and the .NET Framework evaluate Nothing differently when it comes to strings.
Visual Basic Runtime and the .NET Framework
Consider the following example:
Dim MyString As String = "This is my string"
Dim stringLength As Integer
' Explicitly set the string to Nothing.
MyString = Nothing
' stringLength = 0
stringLength = Len(MyString)
' This line, however, causes an exception to be thrown.
stringLength = MyString.Length
The Visual Basic runtime usually evaluates Nothing as an empty string (""). The .NET Framework does not, however, and throws an exception whenever an attempt is made to perform a string operation on Nothing.