ThreadLocal<T> Class

Provides thread-local storage of data.

System.Object
  System.Threading.ThreadLocal<T>

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

[HostProtectionAttribute(SecurityAction.LinkDemand, Synchronization = true, 
	ExternalThreading = true)]
public class ThreadLocal<T> : IDisposable

Type Parameters

T

Specifies the type of data stored per-thread.

The ThreadLocal<T> type exposes the following members.

  NameDescription
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsThreadLocal<T>()Initializes the ThreadLocal<T> instance.
Public methodSupported in .NET for Windows Store appsThreadLocal<T>(Boolean)Initializes the ThreadLocal<T> instance.
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsThreadLocal<T>(Func<T>)Initializes the ThreadLocal<T> instance with the specified valueFactory function.
Public methodSupported in .NET for Windows Store appsThreadLocal<T>(Func<T>, Boolean)Initializes the ThreadLocal<T> instance with the specified valueFactory function.
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  NameDescription
Public propertySupported by Portable Class LibrarySupported in .NET for Windows Store appsIsValueCreatedGets whether Value is initialized on the current thread.
Public propertySupported by Portable Class LibrarySupported in .NET for Windows Store appsValueGets or sets the value of this instance for the current thread.
Public propertySupported in .NET for Windows Store appsValuesGets a list for all of the values currently stored by all of the threads that have accessed this instance.
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  NameDescription
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsDispose()Releases all resources used by the current instance of the ThreadLocal<T> class.
Protected methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsDispose(Boolean)Releases the resources used by this ThreadLocal<T> instance.
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsFinalizeReleases the resources used by this ThreadLocal<T> instance. (Overrides Object.Finalize().)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsToStringCreates and returns a string representation of this instance for the current thread. (Overrides Object.ToString().)
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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.

The following example shows how to use ThreadLocal<T>:

using System;
using System.Threading;
using System.Threading.Tasks;

class ThreadLocalDemo
{

        // Demonstrates: 
        //      ThreadLocal(T) constructor 
        //      ThreadLocal(T).Value 
        //      One usage of ThreadLocal(T) 
        static void Main()
        {
            // Thread-Local variable that yields a name for a thread
            ThreadLocal<string> ThreadName = new ThreadLocal<string>(() =>
            {
                return "Thread" + Thread.CurrentThread.ManagedThreadId;
            });

            // Action that prints out ThreadName for the current thread
            Action action = () =>
            {
                // If ThreadName.IsValueCreated is true, it means that we are not the 
                // first action to run on this thread. 
                bool repeat = ThreadName.IsValueCreated;

                Console.WriteLine("ThreadName = {0} {1}", ThreadName.Value, repeat ? "(repeat)" : "");
            };

            // Launch eight of them.  On 4 cores or less, you should see some repeat ThreadNames
            Parallel.Invoke(action, action, action, action, action, action, action, action);

            // Dispose when you are done
            ThreadName.Dispose();
        }
}

.NET Framework

Supported in: 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

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

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.

With the exception of Dispose, all public and protected members of ThreadLocal<T> thread-safe and may be used concurrently from multiple threads. The value returned for the Value and IsValueCreated properties is specific for the thread on which the property is accessed.

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