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
Parameters
- Expression
Required. Object expression.
Remarks
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.
Example
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.
Requirements
Namespace: Microsoft.VisualBasic
Module: Information
Assembly: Visual Basic Runtime Library (in Microsoft.VisualBasic.dll)
See Also
Reference
IsArray Function (Visual Basic)
IsDate Function (Visual Basic)