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POHow to use DangerousAddRef when async native call
 

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  1. POHow to use DangerousAddRef when async native call
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    <p>When calling a native function that takes IntPtr I understand how to do it with a Sync native function.</p> <pre><code> [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)] public static void Operation(SafeHandle handle) { var mustReleaseSafeHandle = false; RuntimeHelpers.PrepareConstrainedRegions(); try { handle.DangerousAddRef(ref mustReleaseSafeHandle); if (mustReleaseSafeHandle) WinAPI.Operation(handle.DangerousGetHandle()); } finally { if (mustReleaseSafeHandle) handle.DangerousRelease(); } } </code></pre> <p>How do I ensure the DangerousRelease happens when the native function is async?</p> <p>Here is a pseudo example of my async attempt to add more context as Hans Passant suggests.</p> <pre><code> public static unsafe void Operation(SafeHandle fileHandle, SafeHandle nativeMemoryHandle, int offset) { var mustReleaseSafeHandle = false; var ioCompletionCallback = new IOCompletionCallback((code, bytes, overlap) =&gt; { if (mustReleaseSafeHandle) nativeMemoryHandle.DangerousRelease(); Overlapped.Free(overlap); }); var overlapped = new Overlapped(); var nativeOverlapped = overlapped.Pack(ioCompletionCallback, null); nativeMemoryHandle.DangerousAddRef(ref mustReleaseSafeHandle); if (mustReleaseSafeHandle) { var memoryStartLocation = IntPtr.Add(nativeMemoryHandle.DangerousGetHandle(), offset); if (!WinAPI.Operation(fileHandle, memoryStartLocation, offset, nativeOverlapped)) { nativeMemoryHandle.DangerousRelease(); Overlapped.Free(nativeOverlapped); } } else { Overlapped.Free(nativeOverlapped); } } </code></pre>
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    1. PTQuestion
    1. USAaron Stainback
    1. USAaron Stainback
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    1. COClearly you should call it when the native function is completed. You left no breadcrumbs at all to give specific advice beyond that.
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      1. POHow to use DangerousAddRef when async native call
      1. USHans Passant
    2. COSo the native function will call back into the CLR because it's using a IOCompletionCallback and ThreadPool.BindHandle. I know that I can call it in the callback but is that reliable? Without being in a CER I imagine it could fail because of async exceptions.
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      1. POHow to use DangerousAddRef when async native call
      1. USAaron Stainback
 

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