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Information.IsDBNull Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Returns a Boolean value indicating whether an expression evaluates to the System.DBNull class.

Namespace:  Microsoft.VisualBasic
Assembly:  Microsoft.VisualBasic (in Microsoft.VisualBasic.dll)

Syntax

'Declaration
Public Shared Function IsDBNull ( _
    Expression As Object _
) As Boolean

public static bool IsDBNull(
    Object Expression
)

Parameters

Return Value

Type: System.Boolean
Returns a Boolean value indicating whether an expression evaluates to the System.DBNull class.

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.

Examples

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.

Version Information

Silverlight

Supported in: 5, 4, 3

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.