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Nullable(Of T).HasValue Property


Gets a value indicating whether the current Nullable(Of T) object has a valid value of its underlying type.

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

Public ReadOnly Property HasValue As Boolean

Property Value

Type: System.Boolean

true if the current Nullable(Of T) object has a value; false if the current Nullable(Of T) object has no value.

If the HasValue property is true, the value of the current Nullable(Of T) object can be accessed with the Value property. Otherwise, attempting to access its value throws an InvalidOperationException exception.

The following example uses the HasValue property of a Nullable<Integer> object to determine whether it should display the object's Value property or its GetValueOrDefault property.

Module Example
   Public Sub Main()
      Dim n1 As New Nullable(Of Integer)(10)
      Dim n2 As Nullable(Of Integer)
      Dim n3 As New Nullable(Of Integer)(20)
      n3 = Nothing
      Dim items() As Nullable(Of Integer) = { n1, n2, n3 }

      For Each item In items
         Console.WriteLine("Has a value: {0}", item.HasValue)
         If item.HasValue Then
            Console.WriteLine("Type: {0}", item.GetType().Name)
            Console.WriteLine("Value: {0}", item.Value)
            Console.WriteLine("Null: {0}", item Is Nothing)
            Console.WriteLine("Default Value: {0}", item.GetValueOrDefault())
         End If
   End Sub
End Module
' The example displays the following output:
'       Has a value: True
'       Type: Int32
'       Value: 10
'       Has a value: False
'       Null: True
'       Default Value: 0
'       Has a value: False
'       Null: True
'       Default Value: 0

Universal Windows Platform
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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