ReaderWriterLockSlim.EnterWriteLock Method


Tries to enter the lock in write mode.

 void EnterWriteLock();
public void EnterWriteLock ();
member this.EnterWriteLock : unit -> unit
Public Sub EnterWriteLock ()


The RecursionPolicy property is NoRecursion and the current thread has already entered the lock in any mode.


The current thread has entered read mode and doesn't already own a write lock, so trying to enter the lock in write mode would create the possibility of a deadlock.


The recursion number would exceed the capacity of the counter. The limit is so large that applications should never encounter it.

The ReaderWriterLockSlim object has been disposed.


The following example shows how to use the EnterWriteLock method to enter the lock in write mode. The method shown in the example adds a new key/value pair to the synchronized cache. If the key is already in the cache, the exception thrown by the inner Dictionary<TKey,TValue> is allowed to terminate the method. A finally block is used to execute the ExitWriteLock method, ensuring that the caller exits write mode.

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

private ReaderWriterLockSlim cacheLock = new ReaderWriterLockSlim();
private Dictionary<int, string> innerCache = new Dictionary<int, string>();
Private cacheLock As New ReaderWriterLockSlim()
Private innerCache As New Dictionary(Of Integer, String)
public void Add(int key, string value)
        innerCache.Add(key, value);
Public Sub Add(ByVal key As Integer, ByVal value As String)
        innerCache.Add(key, value)
    End Try
End Sub


This method blocks until the calling thread enters the lock, and therefore might never return. Use the TryEnterWriteLock method to block for a specified interval, and then return if the calling thread has not entered write mode during that interval.

If other threads have entered the lock in read mode, a thread that calls the EnterWriteLock method blocks until those threads have exited read mode. When there are threads waiting to enter write mode, additional threads that try to enter read mode or upgradeable mode block until all the threads waiting to enter write mode have either timed out or entered write mode and then exited from it.


If a lock allows recursion, a thread that has entered the lock in write mode can enter write mode recursively, even if other threads are waiting to enter write mode.

Applies to