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PODllImport - function not returning the correct value in ASP.Net when deployed to IIS
 

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  1. PODllImport - function not returning the correct value in ASP.Net when deployed to IIS
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    <p>I have a web service that I need to make a call to a function in some unmanaged code, I import the dll like:</p> <pre><code> class myClass { [DllImport("mydll.dll")] public static extern int FetchMyData(int DataType, int DataIndex); } </code></pre> <p>The web page does an AJAX callback to a WebService which calls the imported function like:</p> <pre><code> [WebMethod] public int FetchData(int IndexValue) { return myClass.FetchMyData(DATA_TYPE, IndexValue); } </code></pre> <p>When I run this from VisualStudio using the development IIS Express, everything works fine, and the function returns a positive integer. However, when I deploy to my local IIS, the function always returns -1. It doesn't even throw an exception which seems a bit odd.</p> <p>Things I have tried but didn't make any difference:</p> <ul> <li>added the "IIS AppPool\DefaultAppPool" to the parent directory with full permissions </li> <li>set the "Enable 32-Bit Applications" property to <strong>True</strong></li> </ul> <p><strong>EDIT</strong></p> <p>After further investigation and help from the various comments below it became clear that the issue here was not the function failing, rather a permissions related issue with what the dll function was doing, namely accessing a Memory Mapped File. I have created <a href="https://stackoverflow.com/questions/20363839/opening-a-memory-mapped-file-causes-filenotfoundexception-when-deployed-in-iis">this follow-up post</a> which replicates the core problem with sample code.</p>
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    1. USCommunity
    1. USSausageFingers
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    1. CODid you ask [permissions to execute unmanaged code](http://msdn.microsoft.com/en-us/library/d0313z05(v=vs.90).aspx), see [here on SO](http://stackoverflow.com/questions/5252738/how-to-call-unmanaged-code-in-asp-net-website-and-host-it-in-iis) for more details (assuming that unmanaged code doesn't access something that needs more rights than what granted to ASP.NET user).
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      1. USAdriano Repetti
    2. COMaybe you should look into the function code?
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      1. PODllImport - function not returning the correct value in ASP.Net when deployed to IIS
      1. USAndrey
    3. COThanks @Adriano - I hadn't asked for any permissions. I added the code from the link but this didn't make any noticeable difference.
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