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Visual Basic
H-L Functions
 IsDBNull Function

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Microsoft Visual Studio 2008/.NET Framework 3.5

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Visual Basic Language Reference
IsDBNull Function

Returns a Boolean value that indicates whether an expression evaluates to the System..::.DBNull class.

Public Function IsDBNull(ByVal Expression As Object) As Boolean
Expression

Required. Object expression.

IsDBNull returns True if the data type of Expression evaluates to the DBNull type; otherwise, IsDBNull returns False.

The System..::.DBNull value indicates that the Object represents missing or nonexistent data. DBNull is not the same as Nothing, which indicates that a variable has not yet been initialized. DBNull is also not the same as a zero-length string (""), which is sometimes referred to as a null string.

This example uses the IsDBNull function to determine if a variable evaluates to DBNull.

Visual Basic
Dim testVar As Object
Dim nullCheck As Boolean
nullCheck = IsDBNull(testVar)
testVar = ""
nullCheck = IsDBNull(testVar)
testVar = System.DBNull.Value
nullCheck = IsDBNull(testVar)
' The first two calls to IsDBNull return False; the third returns True.

Namespace: Microsoft.VisualBasic

Module: Information

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

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