CompareExchange(T) Method (T, T, T)

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
Assembly:  mscorlib (in mscorlib.dll)

public static T CompareExchange<T>(
	ref T location1,
	T value,
	T comparand
where T : class


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).

Type: T

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

Type: T

The value that is compared to the value at location1.

Return Value

Type: T

The original value in location1.

Type Parameters


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

Exception Condition

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.


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.

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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