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Interlocked.CompareExchange Method (Object%, Object, Object)

Compares two objects for reference equality and, if they are equal, replaces one of the objects.

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

public static Object CompareExchange(
	ref Object location1,
	Object value,
	Object comparand
)

Parameters

location1
Type: System.Object%
The destination object that is compared with comparand and possibly replaced.
value
Type: System.Object
The object that replaces the destination object if the comparison results in equality.
comparand
Type: System.Object
The object that is compared to the object at location1.

Return Value

Type: System.Object
The original value in location1.

ExceptionCondition
ArgumentNullException

The address of location1 is a null pointer.

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

Beginning with .NET Framework version 2.0, the CompareExchange<T>(T, T, T) method overload provides a type-safe alternative for reference types.

NoteNote

The objects are compared for reference equality, rather than Object.Equals. As a result, two boxed instances of the same value type (for example, the integer 3) always appear to be unequal, and no operation is performed. Do not use this overload with value types.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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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