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POHow to properly return values from unmanaged interface method?
 

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  1. POHow to properly return values from unmanaged interface method?
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    <p>I'm in the process of extending GeckoFx (http://geckofx.org) and am having some problems returning array values from unmanaged interfaces provided by XPCom.</p> <p>I've added a great amount of new feature support to GeckoFx using the latest XulRunner 1.9.2.13 build but, I'm getting access violation exceptions when attempting to return arrays from interface methods. Eg:</p> <pre><code>[Guid("43987F7B-0FAA-4019-811E-42BECAC73FC5"), ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown)] interface mozISpellCheckingEngine { //... void GetDictionaryList([MarshalAs(UnmanagedType.LPArray, ArraySubType=UnmanagedType.LPWStr)]ref string[] dictionaries, out uint count); //... } public static string[] GetAvailableDictionaries() { string[] _dictionaries = null; uint count = 0; //GetSpellChecker() returns a valid mozISpellCheckingEngine object GetSpellChecker().GetDictionaryList(ref _dictionaries, out count); if (count &gt; 0) { if (_dictionaries != null) { return _dictionaries; } } return null; } </code></pre> <p>The problem is when GetDictionaryList returns sometimes it will return a list with a single index and containing the name of one dictionary (I have 2 dictionaries in the location this method searches in) and count returns with the correct value of 2; other times the method will fail and throw an access violation and the value of _dictionaries is string[0] while count remains correct with the value of 2.</p> <p>I guess the biggest part of this question would have to be 'Am I marshaling the method and its parameters correctly in the interface declaration?'.</p> <p>This example code is just that - an example. There are several other XulRunner features I would like to implement in GeckoFx but, they return arrays as well and suffer from the same problem. Until I can get past this issue my work is at a bit of a stand-still.</p> <p>Thanks for any and all help you can provide.</p> <p>-Scott</p>
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    1. COTry dropping the `ref` keyword from the array argument, since that implies pointer-to-pointer-to-data (arrays are implicitly pointers in C#), and my guess is the interface specifies pointer-to-data (as is common for C arrays).
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    2. COdid you have access to unmanage code to edit it?
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      1. USSaeed Amiri
 

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