Artikel
11/18/2011

Nullable<T>.Value Property

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

Gets the value of the current Nullable<T> value.

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

Syntax

'Declaration
Public ReadOnly Property Value As T

public T Value { get; }

Property Value

Type: T
The value of the current Nullable<T> object if the HasValue property is true. An exception is thrown if the HasValue property is false.

Exceptions

Exception	Condition
InvalidOperationException	The HasValue property is false.

Examples

The following code example returns the value of a Nullable<T> 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.


Class Example
   Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
      Dim myNow As Nullable(Of DateTime)

      '  Assign the current date and time to myNow then display its value.
      myNow = DateTime.Now
      Display(outputBlock, myNow, "1) ")

      '  Assign null (Nothing in Visual Basic) to myNow then display its value.
      myNow = Nothing
      Display(outputBlock, myNow, "2) ")
   End Sub 'Main

   ' Display the date and time.
   Public Shared Sub Display(ByVal outputBlock As System.Windows.Controls.TextBlock, 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.
      outputBlock.Text &= title
      If displayDateTime.HasValue = True Then
         outputBlock.Text += String.Format("The date and time is {0:F}.", displayDateTime.Value) & vbCrLf
      Else
         outputBlock.Text &= "The date and time is not defined." & vbCrLf
      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.
'

// This code example demonstrates the Nullable<T>.HasValue 
// and Value properties.

using System;

class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      DateTime? myNow;

      //  Assign the current date and time to myNow then display its value.
      myNow = DateTime.Now;
      Display(outputBlock, myNow, "1) ");

      //  Assign null (Nothing in Visual Basic) to myNow then display its value.
      myNow = null;
      Display(outputBlock, myNow, "2) ");
   }

   // Display the date and time.
   public static void Display(System.Windows.Controls.TextBlock outputBlock, DateTime? displayDateTime, string title)
   {
      // If a value is defined for the displayDatetime argument, display its value; otherwise, 
      // display that no value is defined.
      outputBlock.Text += title;
      if (displayDateTime.HasValue == true)
         outputBlock.Text += String.Format("The date and time is {0:F}.", displayDateTime.Value) + "\n";
      else
         outputBlock.Text += "The date and time is not defined." + "\n";
   }
}

/*
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.

*/

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

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

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