Nullable<T>.HasValue Property
Microsoft Silverlight will reach end of support after October 2021. Learn more.
Gets a value indicating whether the current Nullable<T> object has a value.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public ReadOnly Property HasValue As Boolean
public bool HasValue { get; }
Property Value
Type: System.Boolean
true if the current Nullable<T> object has a value; false if the current Nullable<T> object has no value.
Remarks
If the HasValue property is true, the value of the current Nullable<T> object can be accessed with the Value property.
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.