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Nullable.HasValue Property

Gets a value indicating whether the current Nullable object has a value.

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

'Declaration
Public ReadOnly Property HasValue As Boolean
'Usage
Dim instance As Nullable(Of T)
Dim value As Boolean

value = instance.HasValue

/** @property */
public boolean get_HasValue ()

public function get HasValue () : boolean

Not applicable.

Property Value

true if the current Nullable object has a value; false if the current Nullable object has no value.

If the HasValue property is true, the value of the current Nullable object can be accessed with the Value property.

The following code example returns the value of a Nullable object if that object has a defined value; otherwise, a default value is returned.

' This code example demonstrates the Nullable(Of T).HasValue 
' and Value properties.

Imports System

Class Sample
    Public Shared Sub Main() 
        Dim myNow As Nullable(Of DateTime)

    '  Assign the current date and time to myNow then display its value.
        myNow = DateTime.Now
        Display(myNow, "1) ")
        
    '  Assign null (Nothing in Visual Basic) to myNow then display its value.
        myNow = Nothing
        Display(myNow, "2) ")
    End Sub 'Main
    
    ' Display the date and time.
    Public Shared Sub Display(ByVal displayDateTime As Nullable(Of DateTime), _
                              ByVal title As String) 

    ' If the HasValue property for the nullable of DateTime input argument is true, 
    ' display the value of the input argument; otherwise, display that no value is
    ' defined for the input value.
        Console.Write(title)
        If displayDateTime.HasValue = True Then
            Console.WriteLine("The date and time is {0:F}.", displayDateTime.Value)
        Else
            Console.WriteLine("The date and time is not defined.")
        End If
    End Sub 'Display 

End Class 'Sample '

'This code example produces the following results:
'
'1) The date and time is Tuesday, April 19, 2005 4:16:06 PM.
'2) The date and time is not defined.
'

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

.NET Compact Framework

Supported in: 2.0

XNA Framework

Supported in: 1.0

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