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POC# ReaderWriterLockSlim Best Practice to Avoid Recursion
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copied!<p>I have a class using <a href="http://msdn.microsoft.com/en-us/library/system.threading.readerwriterlockslim.aspx" rel="noreferrer">ReaderWriterLockSlim</a> with a read method and a write method that uses the read method to retrieve the element to be modified. A quick example would be:</p> <pre><code>class FooLocker { ReaderWriterLockSlim locker = new ReaderWriterLockSlim(); List<Foo> fooList = new List<Foo>(); public void ChangeFoo(int index, string bar) { locker.EnterWriteLock(); try { Foo foo = GetFoo(index); foo.Bar = bar; } finally { locker.ExitWriteLock(); } } public Foo GetFoo(int index) { locker.EnterReadLock(); //throws System.Threading.LockRecursionException try { return fooList[index]; } finally { locker.ExitReadLock(); } } //snipped code for adding instances etc. } </code></pre> <p>As above, this code throws a <code>LockRecursionException</code> when calling <code>ChangeFoo()</code> because a write lock is already held when <code>GetFoo()</code> tries to enter a read lock.</p> <p>I've checked the documentation for <code>ReaderWriterLockSlim</code> and I can use <code>LockRecursionPolicy.SupportsRecursion</code> to allow the above to work. However, the documentation also recommends that this shouldn't be used for any new development and should only be used when upgrading existing code.</p> <p>Given this, what is the best practice to achieve the same result where a write method can use a read-only method to retrieve the thing that needs to be modified?</p>

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