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When you call <code>makeNewHandleOfA</code>, you own the returned instance, so you must release it. When you call <code>getHandleOfA</code>, you do not own the returned instance, but you still want to manage its lifecyle (ie: prevent the underlying native library from releasing it). It means you basically want different Release strategies for those two use cases. Option 1 With: <pre><code>internal class MyOwnedSafeHandleA : MySafeHandleA { protected override bool ReleaseHandle() { releaseHandleToA(handle); return true; } } internal class MySafeHandleA : SafeHandle { private int refCountIncremented; internal void IncrementRefCount(Action<MySafeHandleA> nativeIncrement) { nativeIncrement(this); refCountIncremented++; } protected override bool ReleaseHandle() { while (refCountIncremented > 0) { releaseHandleToA(handle); refCountIncremented--; } return true; } } </code></pre> You can declare your DllImports like so: <pre><code> [DllImport("somedll.dll")] public extern MyOwnedSafeHandleA makeNewHandleOfA(); [DllImport("somedll.dll")] private extern MySafeHandleA getHandleOfA(MySafeHandleB handleToB, int index); [DllImport("somedll.dll")] private extern void addRefHandleToA(MySafeHandleA handleToA); </code></pre> Option 2 You could declare your SafeHandle like this: <pre><code>internal class MySafeHandleA : SafeHandle { MySafeHandleA(IntPtr handle) : base(IntPtr.Zero, true) { SetHandle(handle); } protected override bool ReleaseHandle() { releaseHandleToA(handle); return true; } } </code></pre> And use it like so: <pre><code>[DllImport("somedll.dll"] private extern IntPtr getHandleOfA(MySafeHandleB handleToB, int index); [DllImport("somedll.dll"] private extern void addRefHandleToA(IntPtr ptr); public MySafeHandleA _getHandleOfA(MySafeHandleB handleToB, int index) { IntPtr ptr = getHandleOfA(handleToB, index); addRefHandleToA(ptr); return new MySafeHandleA(ptr); } </code></pre>
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