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Object.ReferenceEquals Method

Updated: September 2010

Determines whether the specified Object instances are the same instance.

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

'Declaration
Public Shared Function ReferenceEquals ( _
	objA As Object, _
	objB As Object _
) As Boolean
'Usage
Dim objA As Object 
Dim objB As Object 
Dim returnValue As Boolean 

returnValue = Object.ReferenceEquals(objA, _
	objB)

Parameters

objA
Type: System.Object

The first object to compare.

objB
Type: System.Object

The second object to compare.

Return Value

Type: System.Boolean
true if objA is the same instance as objB or if both are null references; otherwise, false.

Unlike the Equals method and the equality operator, the ReferenceEquals method cannot be overridden. Because of this, if you want to test two object references for equality and are unsure about the implementation of the Equals method, you can call the ReferenceEquals method. However, note that if objA and objB are value types, they are boxed before they are passed to the ReferenceEquals method.

The following code example uses ReferenceEquals to determine if two objects are the same instance.

Imports System

Public Class App
    Public Shared Sub Main() 
        Dim o As Object = Nothing 
        Dim p As Object = Nothing 
        Dim q As New Object
        Console.WriteLine(Object.ReferenceEquals(o, p))
        p = q
        Console.WriteLine(Object.ReferenceEquals(p, q))
        Console.WriteLine(Object.ReferenceEquals(o, p))
    End Sub  
End Class  
' This code produces the following output: 

' True 
' True 
' False 
'

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Date

History

Reason

September 2010

Added the Remarks section.

Customer feedback.

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