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Thread.FreeNamedDataSlot Method

Eliminates the association between a name and a slot, for all threads in the process. For better performance, use fields that are marked with the ThreadStaticAttribute attribute instead.

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

[HostProtectionAttribute(SecurityAction.LinkDemand, SharedState = true, ExternalThreading = true)]
public static void FreeNamedDataSlot(
	string name


Type: System.String
The name of the data slot to be freed.

Important noteImportant

The .NET Framework provides two mechanisms for using thread local storage (TLS): thread-relative static fields (that is, fields that are marked with the ThreadStaticAttribute attribute) and data slots. Thread-relative static fields provide much better performance than data slots, and enable compile-time type checking. For more information about using TLS, see Thread Local Storage: Thread-Relative Static Fields and Data Slots.

After any thread calls FreeNamedDataSlot, any other thread that calls GetNamedDataSlot with the same name will allocate a new slot associated with the name. Subsequent calls to GetNamedDataSlot by any thread will return the new slot. However, any thread that still has a System.LocalDataStoreSlot returned by an earlier call to GetNamedDataSlot can continue to use the old slot.

A slot that has been associated with a name is released only when every LocalDataStoreSlot that was obtained prior to the call to FreeNamedDataSlot has been released and garbage-collected.

Threads use a local store memory mechanism to store thread-specific data. The common language runtime allocates a multi-slot data store array to each process when it is created. The thread can allocate a data slot in the data store, store and retrieve a data value in the slot, and free the slot for reuse after the thread expires. Data slots are unique per thread. No other thread (not even a child thread) can get that data.


The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: SharedState | 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.

This section contains two code examples. The first example shows how to use a field that is marked with the ThreadStaticAttribute attribute to hold thread-specific information. The second example shows how to use a data slot to do the same thing.

First Example

The following example shows how to use a field that is marked with ThreadStaticAttribute to hold thread-specific information. This technique provides better performance than the technique that is shown in the second example.

using System;
using System.Threading;

class Test
    static void Main()
        for(int i = 0; i < 3; i++)
            Thread newThread = new Thread(ThreadData.ThreadStaticDemo);

class ThreadData
    static int threadSpecificData;

    public static void ThreadStaticDemo()
        // Store the managed thread id for each thread in the static
        // variable.
        threadSpecificData = Thread.CurrentThread.ManagedThreadId;

        // Allow other threads time to execute the same code, to show
        // that the static data is unique to each thread.
        Thread.Sleep( 1000 );

        // Display the static data.
        Console.WriteLine( "Data for managed thread {0}: {1}", 
            Thread.CurrentThread.ManagedThreadId, threadSpecificData );

/* This code example produces output similar to the following:

Data for managed thread 4: 4
Data for managed thread 5: 5
Data for managed thread 3: 3

Second Example

The following example demonstrates how to use a named data slot to store thread-specific information.

using System;
using System.Threading;

class Test
    public static void Main()
        Thread[] newThreads = new Thread[4];
        int i;
        for (i = 0; i < newThreads.Length; i++)
            newThreads[i] =
                new Thread(new ThreadStart(Slot.SlotTest));
        for (i = 0; i < newThreads.Length; i++)
            Console.WriteLine("Thread_{0} finished.",

class Slot
    private static Random randomGenerator = new Random();

    public static void SlotTest()
        // Set random data in each thread's data slot.
        int slotData = randomGenerator.Next(1, 200);
        int threadId = Thread.CurrentThread.ManagedThreadId;


        // Show what was saved in the thread's data slot.
        Console.WriteLine("Data stored in thread_{0}'s data slot: {1,3}",
            threadId, slotData);

        // Allow other threads time to execute SetData to show
        // that a thread's data slot is unique to itself.

        int newSlotData =

        if (newSlotData == slotData)
            Console.WriteLine("Data in thread_{0}'s data slot is still: {1,3}",
                threadId, newSlotData);
            Console.WriteLine("Data in thread_{0}'s data slot changed to: {1,3}",
                threadId, newSlotData);

.NET Framework

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

.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.