GetValueOrDefault Method
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Nullable(Of T).GetValueOrDefault Method

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Retrieves the value of the current Nullable(Of T) object, or the object's default value.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)

'Declaration
Public Function GetValueOrDefault As T

Return Value

Type: T
The value of the Value property if the HasValue property is true; otherwise, the default value of the current Nullable(Of T) object. The type of the default value is the type argument of the current Nullable(Of T) object, and the value of the default value consists solely of binary zeroes.

The GetValueOrDefault method returns a value even if the HasValue property is false (unlike the Value property, which throws an exception).

The following code example retrieves the value of a Nullable(Of T) object if that value is defined; otherwise, it retrieves the default value or a specific default value.


' This code example demonstrates the 
' Nullable(Of T).GetValueOrDefault methods.


Class Example
    Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
        Dim mySingle As Nullable(Of System.Single) = 12.34F
        Dim yourSingle As Nullable(Of System.Single) = -1.0F

        outputBlock.Text &= "*** Display a value or the default value ***" & vbCrLf
        ' Display the values of mySingle and yourSingle.

        Display(outputBlock, "A1", mySingle, yourSingle)

        outputBlock.Text &= vbCrLf

        yourSingle = mySingle.GetValueOrDefault()
        Display(outputBlock, "A2", mySingle, yourSingle)

        outputBlock.Text &= vbCrLf

        ' Assign null (Nothing in Visual Basic) to mySingle, which means no value is
        ' defined for mySingle. Then assign the value of mySingle to yourSingle and
        ' display the values of both variables. The default value of all binary zeroes 
        ' is assigned to yourSingle because mySingle has no value.
        mySingle = Nothing
        yourSingle = mySingle.GetValueOrDefault()
        Display(outputBlock, "A3", mySingle, yourSingle)
        outputBlock.Text &= vbCrLf

        ' Reassign the original values of mySingle and yourSingle.
        mySingle = 12.34F
        yourSingle = -1.0F

        outputBlock.Text &= vbCrLf & "*** Display a value or the "
        outputBlock.Text &= "specified default value ***" & vbCrLf & vbCrLf

        ' Display the values of mySingle and yourSingle.
        Display(outputBlock, "B1", mySingle, yourSingle)
        outputBlock.Text &= vbCrLf

        ' Assign the value of mySingle to yourSingle, then display the values 
        ' of mySingle and yourSingle. The yourSingle variable is assigned the 
        ' value 12.34 because mySingle has a value.
        yourSingle = mySingle.GetValueOrDefault(-222.22F)
        Display(outputBlock, "B2", mySingle, yourSingle)
        outputBlock.Text &= vbCrLf

        ' Assign null (Nothing in Visual Basic) to mySingle, which means no value is
        ' defined for mySingle. Then assign the value of mySingle to yourSingle and
        ' display the values of both variables. The specified default value of -333.33
        ' is assigned to yourSingle because mySingle has no value.
        mySingle = Nothing
        yourSingle = mySingle.GetValueOrDefault(-333.33F)
        Display(outputBlock, "B3", mySingle, yourSingle)

    End Sub


    ' Display the values of two nullable of System.Single structures.
    ' The Console.WriteLine method automatically calls the ToString methods of 
    ' each input argument to display its values. If no value is defined for a
    ' nullable type, the ToString method for that argument returns the empty
    ' string ("").

    Public Shared Sub Display(ByVal outputBlock As System.Windows.Controls.TextBlock, _
                              ByVal title As String, _
                              ByVal dspMySingle As Nullable(Of System.Single), _
                              ByVal dspYourSingle As Nullable(Of System.Single))
        If (True) Then
            outputBlock.Text += String.Format("{0}) & mySingle = [{1}], yourSingle = [{2}]", _
                               title, dspMySingle, dspYourSingle)
        End If
    End Sub
End Class

'
'This code example produces the following results:
'
'A1) mySingle = [12.34], yourSingle = [-1]
'A2) mySingle = [12.34], yourSingle = [12.34]
'A3) mySingle = [], yourSingle = [0]
'
'*** Display a value or the specified default value ***
'
'B1) mySingle = [12.34], yourSingle = [-1]
'B2) mySingle = [12.34], yourSingle = [12.34]
'B3) mySingle = [], yourSingle = [-333.33]
'


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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