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POIOException getting thrown by ReaderWriteLockSlim?
 

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  1. POIOException getting thrown by ReaderWriteLockSlim?
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    <p>I have a static class which is accessed by multiple threads and uses a ReaderWriterLockSlim in various methods to maintain thread safety. This works fine most of the time, however very intermittently I'm seeing an IOException handle is invalid error being thrown by one particular method as shown in the stack trace below. This has me greatly confused as I didn't even know that System.IO was involved in a ReaderWriterLock.</p> <p>Any help at all in understanding where the error may be comming from would be greatly appreciated.</p> <p>Stack Trace:</p> <blockquote> <p>System.IO.IOException: The handle is invalid.<br> at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)<br> at System.Threading.EventWaitHandle.Reset()<br> at System.Threading.ReaderWriterLockSlim.WaitOnEvent(EventWaitHandle waitEvent, UInt32&amp; numWaiters, Int32 millisecondsTimeout)<br> at System.Threading.ReaderWriterLockSlim.TryEnterUpgradeableReadLock(Int32 millisecondsTimeout)</p> </blockquote> <p>Code:</p> <pre><code>class Class1 { private static ReaderWriterLockSlim readwriteLock = new ReaderWriterLockSlim(); private const int readwriterlocktimeoutms = 5000; private static void myMethod(int ID) { bool IsTaken = false; bool isWriteLockTaken = false; if (!readwriteLock.TryEnterUpgradeableReadLock(readwriterlocktimeoutms)) { throw new Exception("SafeGetSuItem: Error acquiring read lock"); } else { IsTaken = true; } try { // do some work which may require upgrading to a write lock depending on particular conditions } finally { if (IsTaken) { try { readwriteLock.ExitUpgradeableReadLock(); IsTaken = false; } catch { throw; } } } } } enter code here bool IsWriteTaken = false; try { if (!readerwriterlock.TryEnterWriteLock(readerwriterlocktimeout)) { // log the error } else { IsWriteTaken = true; } if (IsWriteTaken) { // do some work } } finally { if (IsWriteTaken) { try { readerwriterlock.ExitWriteLock(); } catch { throw; } } } </code></pre>
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    1. USJohnv2020
    1. USJohnv2020
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    1. COThat doesn't seem logical, but is there any File I/O going on inside the try blocks?
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      1. USHenk Holterman
    2. COAnd OT, there is no way to get in the finally block with IsTaken==false, and `catch {throw; }` can also be missed. Simplify your code and less can go wrong.
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      1. USHenk Holterman
    3. COIt looks to me like something else is disposing the reader/writer lock instance while your code is in the middle of trying to obtain the read lock. That destroys the `ReaderWriterLockSlim` instance's internal `EventWaitHandle`.
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      1. USJim Mischel
 

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