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IsNothing Function

Visual Studio 2008

Returns a Boolean value indicating whether an expression has no object assigned to it.

Public Function IsNothing(ByVal Expression As Object) As Boolean


Required. Object expression.

IsNothing returns True if the expression represents an object variable that currently has no object assigned to it; otherwise, it returns False.

IsNothing is intended to work on reference types. A value type cannot hold a value of Nothing and reverts to its default value if you assign Nothing to it. If you supply a value type in Expression, IsNothing always returns False.

The following example uses the IsNothing function to determine if an object variable is associated with any object instance.

Dim testVar As Object 
' No instance has been assigned to variable testVar yet. 
Dim testCheck As Boolean 
' The following call returns True.
testCheck = IsNothing(testVar)
' Assign a string instance to variable testVar.
testVar = "ABCDEF" 
' The following call returns False.
testCheck = IsNothing(testVar)
' Disassociate variable testVar from any instance.
testVar = Nothing 
' The following call returns True.
testCheck = IsNothing(testVar)

Namespace: Microsoft.VisualBasic

Module: Information

Assembly: Visual Basic Runtime Library (in Microsoft.VisualBasic.dll)