Статья
11/18/2011

Guid.Empty Field

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

A read-only instance of the Guid class whose value is guaranteed to be all zeroes.

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

Syntax

'Declaration
Public Shared ReadOnly Empty As Guid

public static readonly Guid Empty

Remarks

You can compare a GUID with the value of the Guid.Empty field to determine whether a GUID is non-zero. The following example uses the Equality operator to compare two GUID values with Guid.Empty to determine whether they consist exclusively of zeros.

Module Example
   Public Sub Demo(outputBlock As System.Windows.Controls.TextBlock)
      ' Create a GUID and determine whether it consists of all zeros.
      Dim guid1 As Guid = Guid.NewGuid
      outputBlock.Text += guid1.ToString() + vbCrLf
      outputBlock.Text += String.Format("Empty: {0}", guid1 = Guid.Empty) + vbCrLf
      outputBlock.Text += vbCrLf

      ' Create a GUID with all zeros and compare it to Empty.
      Dim bytes(15) As Byte
      Dim guid2 As New Guid(bytes)
      outputBlock.Text += guid2.ToString() + vbCrLf
      outputBlock.Text += String.Format("Empty: {0}", guid2 = Guid.Empty) + vbCrLf
   End Sub
End Module
' The example displays output like the following:
'       11c43ee8-b9d3-4e51-b73f-bd9dda66e29c
'       Empty: False
'       
'       00000000-0000-0000-0000-000000000000
'       Empty: True

using System;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      // Create a GUID and determine whether it consists of all zeros.
      Guid guid1 = Guid.NewGuid();
      outputBlock.Text += guid1.ToString() + "\n";
      outputBlock.Text += String.Format("Empty: {0}\n\n", guid1 == Guid.Empty);

      // Create a GUID with all zeros and compare it to Empty.
      Byte[] bytes = new Byte[16];
      Guid guid2 = new Guid(bytes);
      outputBlock.Text += guid2.ToString() + "\n";
      outputBlock.Text += String.Format("Empty: {0}\n", guid2 == Guid.Empty);
   }
}
// The example displays output like the following:
//       11c43ee8-b9d3-4e51-b73f-bd9dda66e29c
//       Empty: False
//       
//       00000000-0000-0000-0000-000000000000
//       Empty: True

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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