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.

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)

See Also


IsArray Function (Visual Basic)

IsDate Function (Visual Basic)

IsError Function

IsNothing Function

IsNumeric Function (Visual Basic)

IsReference Function

Object Data Type


TypeName Function (Visual Basic)