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Thread.SpinWait Method

Causes a thread to wait the number of times defined by the iterations parameter.

Namespace:  System.Threading
Assembly:  mscorlib (in mscorlib.dll)
[HostProtectionAttribute(SecurityAction.LinkDemand, Synchronization = true, 
	ExternalThreading = true)]
public static void SpinWait(
	int iterations
)

Parameters

iterations
Type: System.Int32

A 32-bit signed integer that defines how long a thread is to wait.

The SpinWait method is useful for implementing locks. Classes in the .NET Framework, such as Monitor and ReaderWriterLock, use this method internally. SpinWait essentially puts the processor into a very tight loop, with the loop count specified by the iterations parameter. The duration of the wait therefore depends on the speed of the processor.

Contrast this with the Sleep method. A thread that calls Sleep yields the rest of its current slice of processor time, even if the specified interval is zero. Specifying a non-zero interval for Sleep removes the thread from consideration by the thread scheduler until the time interval has elapsed.

SpinWait is not generally useful for ordinary applications. In most cases, you should use the synchronization classes provided by the .NET Framework; for example, call Monitor.Enter or a statement that wraps Monitor.Enter (lock in C# or SyncLock in Visual Basic).

Caution noteCaution

In the rare case where it is advantageous to avoid a context switch, such as when you know that a state change is imminent, make a call to the SpinWait method in your loop. The code SpinWait executes is designed to prevent problems that can occur on computers with multiple processors. For example, on computers with multiple Intel processors employing Hyper-Threading technology, SpinWait prevents processor starvation in certain situations.

NoteNote

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: Synchronization | ExternalThreading. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

.NET Framework

Supported in: 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

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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