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Interlocked.CompareExchange(T) Method (T, T, T)

Compares two instances of the specified reference type T for equality and, if they are equal, replaces the first one.

Namespace:  System.Threading
Assemblies:   System.Threading (in System.Threading.dll)
  mscorlib (in mscorlib.dll)

static member CompareExchange : 
        location1:'T byref * 
        value:'T * 
        comparand:'T -> 'T  when 'T : not struct

Type Parameters

T

The type to be used for location1, value, and comparand. This type must be a reference type.

Parameters

location1
Type: T

The destination, whose value is compared with comparand and possibly replaced. This is a reference parameter (ref in C#, ByRef in Visual Basic).

value
Type: T

The value that replaces the destination value if the comparison results in equality.

comparand
Type: T

The value that is compared to the value at location1.

Return Value

Type: T
The original value in location1.

ExceptionCondition
NullReferenceException

The address of location1 is a null pointer.

If comparand and the value in location1 are equal, then value is stored in location1. Otherwise, no operation is performed. The comparison and the exchange are performed as an atomic operation. The return value of this method is the original value in location1, whether or not the exchange takes place.

This method only supports reference types. There are overloads of the CompareExchange method for the value types Int32, Int64, IntPtr, Single, and Double, but there is no support for other value types.

NoteNote

This method overload is preferable to the CompareExchange(Object, Object, Object) method overload, because the latter requires the destination object to be accessed late-bound.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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