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ReaderWriterLock.ReleaseLock Method

Releases the lock, regardless of the number of times the thread acquired the lock.

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

public LockCookie ReleaseLock()

Return Value

Type: System.Threading.LockCookie
A LockCookie value representing the released lock.

ReleaseLock releases the reader lock or writer lock, regardless of the recursive lock count. To restore the state of the lock, including the lock count, pass the LockCookie to RestoreLock.

The following code example shows how to use the ReleaseLock method to release the lock, regardless of how many times it has been acquired by the thread, and how to restore the state of the lock later.

This code is part of a larger example provided for the ReaderWriterLock class.

// The complete code is located in the ReaderWriterLock
// class topic.
using System;
using System.Threading;

public class Test
    // Declaring the ReaderWriterLock at the class level
    // makes it visible to all threads.
    static ReaderWriterLock rwl = new ReaderWriterLock();
    // For this example, the shared resource protected by the
    // ReaderWriterLock is just an integer.
    static int resource = 0;


// Shows how to release all locks and later restore
// the lock state. Shows how to use sequence numbers
// to determine whether another thread has obtained
// a writer lock since this thread last accessed the
// resource.
static void ReleaseRestore(int timeOut)
    int lastWriter;

            // It is safe for this thread to read from
            // the shared resource. Cache the value. (You
            // might do this if reading the resource is
            // an expensive operation.)
            int resourceValue = resource;
            Display("reads resource value " + resourceValue); 
            Interlocked.Increment(ref reads);

            // Save the current writer sequence number.
            lastWriter = rwl.WriterSeqNum;

            // Release the lock, and save a cookie so the
            // lock can be restored later.
            LockCookie lc = rwl.ReleaseLock();

            // Wait for a random interval (up to a 
            // quarter of a second), and then restore
            // the previous state of the lock. Note that
            // there is no time-out on the Restore method.
            rwl.RestoreLock(ref lc);

            // Check whether other threads obtained the
            // writer lock in the interval. If not, then
            // the cached value of the resource is still
            // valid.
            if (rwl.AnyWritersSince(lastWriter))
                resourceValue = resource;
                Interlocked.Increment(ref reads);
                Display("resource has changed " + resourceValue);
                Display("resource has not changed " + resourceValue);
            // Ensure that the lock is released.
    catch (ApplicationException)
        // The reader lock request timed out.
        Interlocked.Increment(ref readerTimeouts);



Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

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