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Thread.VolatileRead Method (UInt64%)

.NET Framework 4

Updated: May 2011

Reads the value of a field. The value is the latest written by any processor in a computer, regardless of the number of processors or the state of processor cache.

This API is not CLS-compliant.

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

Syntax

C++

[CLSCompliantAttribute(false)]
public static ulong VolatileRead(
	ref ulong address
)

Parameters

address: Type: System.UInt64%
The field to be read.

Return Value

Type: System.UInt64
The latest value written to the field by any processor.

Remarks

VolatileRead and VolatileWrite are for special cases of synchronization. Under normal circumstances, the C# lock statement, the Visual Basic SyncLock statement, and the Monitor class provide easier alternatives.

On a multiprocessor system, VolatileRead obtains the very latest value written to a memory location by any processor. This might require flushing processor caches.

Even on a uniprocessor system, VolatileRead and VolatileWrite ensure that a value is read or written to memory, and not cached (for example, in a processor register). Thus, you can use them to synchronize access to a field that can be updated by another thread, or by hardware.

Calling this method affects only a single memory access. To provide effective synchronization for a field, all access to the field must use VolatileRead or VolatileWrite.

Version Information

.NET Framework

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

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Platforms

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.