ThreadLocal<T> Class

Reference

Definition

Namespace:: System.Threading

Assembly:: System.Threading.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: ThreadLocal.cs

Source:: ThreadLocal.cs

Source:: ThreadLocal.cs

Important

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Provides thread-local storage of data.

generic <typename T>
public ref class ThreadLocal : IDisposable

public class ThreadLocal<T> : IDisposable

type ThreadLocal<'T> = class
    interface IDisposable

Public Class ThreadLocal(Of T)
Implements IDisposable

Type Parameters

T

Specifies the type of data stored per-thread.

Inheritance: Object
ThreadLocal<T>

Implements: IDisposable

Examples

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();
        }
}
// This multithreading example can produce different outputs for each 'action' invocation and will vary with each run.
// Therefore, the example output will resemble but may not exactly match the following output (from a 4 core processor):
// ThreadName = Thread5 
// ThreadName = Thread6 
// ThreadName = Thread4 
// ThreadName = Thread6 (repeat)
// ThreadName = Thread1 
// ThreadName = Thread4 (repeat)
// ThreadName = Thread7 
// ThreadName = Thread5 (repeat)

Imports System.Threading
Imports System.Threading.Tasks

Module ThreadLocalDemo

    ' Demonstrates:
    ' ThreadLocal(T) constructor
    ' ThreadLocal(T).Value
    ' One usage of ThreadLocal(T)
    Sub Main()
        ' Thread-Local variable that yields a name for a thread
        Dim ThreadName As New ThreadLocal(Of String)(
            Function()
                Return "Thread" & Thread.CurrentThread.ManagedThreadId
            End Function)

        ' Action that prints out ThreadName for the current thread
        Dim action As Action =
            Sub()
                ' If ThreadName.IsValueCreated is true, it means that we are not the
                ' first action to run on this thread.
                Dim repeat As Boolean = ThreadName.IsValueCreated

                Console.WriteLine("ThreadName = {0} {1}", ThreadName.Value, If(repeat, "(repeat)", ""))
            End Sub

        ' 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()
    End Sub
End Module
' This multithreading example can produce different outputs for each 'action' invocation and will vary with each run.
' Therefore, the example output will resemble but may not exactly match the following output (from a 4 core processor):
' ThreadName = Thread5 
' ThreadName = Thread6 
' ThreadName = Thread4 
' ThreadName = Thread6 (repeat)
' ThreadName = Thread1 
' ThreadName = Thread4 (repeat)
' ThreadName = Thread7 
' ThreadName = Thread5 (repeat)

Constructors

ThreadLocal<T>()	Initializes the ThreadLocal<T> instance.
ThreadLocal<T>(Boolean)	Initializes the ThreadLocal<T> instance and specifies whether all values are accessible from any thread.
ThreadLocal<T>(Func<T>, Boolean)	Initializes the ThreadLocal<T> instance with the specified `valueFactory` function and a flag that indicates whether all values are accessible from any thread.
ThreadLocal<T>(Func<T>)	Initializes the ThreadLocal<T> instance with the specified `valueFactory` function.

Properties

IsValueCreated	Gets whether Value is initialized on the current thread.
Value	Gets or sets the value of this instance for the current thread.
Values	Gets a list containing the values stored by all threads that have accessed this instance.

Methods

Dispose()	Releases all resources used by the current instance of the ThreadLocal<T> class.
Dispose(Boolean)	Releases the resources used by this ThreadLocal<T> instance.
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
Finalize()	Releases the resources used by this ThreadLocal<T> instance.
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Creates and returns a string representation of this instance for the current thread.

Applies to

Thread Safety

With the exception of Dispose(), all public and protected members of ThreadLocal<T> are 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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