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Interlocked.CompareExchange Method (Int64%, Int64, Int64)

Compares two 64-bit signed integers for equality and, if they are equal, replaces one of the values.

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

public static long CompareExchange(
	ref long location1,
	long value,
	long comparand


Type: System.Int64%
The destination, whose value is compared with comparand and possibly replaced.
Type: System.Int64
The value that replaces the destination value if the comparison results in equality.
Type: System.Int64
The value that is compared to the value at location1.

Return Value

Type: System.Int64
The original value in location1.


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 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.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.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.