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POPass reference of struct in a list from managed to unmanaged code across dll
 

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  1. POPass reference of struct in a list from managed to unmanaged code across dll
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    <p>I am very new to C# and currently having some trouble with marshalling structs to C functions in a dll. The struct in question contains a few ints, float and one char* in C as follows:</p> <pre><code>struct Bin { char* m_name; float m_start; float m_end; int m_OwnerID; int m_SelfID; } </code></pre> <p>The corresponding C# struct defintion, I think should be:</p> <pre><code>public struct Bin { public string m_name; public float m_start; public float m_end; public int m_OwnerID; public int m_SelfID; } </code></pre> <p>I also implemented a parser/reader function in C# that reads a text file, creates the Bin objects and stores them in a List object, which is a class member of the main app class. At the same time, I want to pass references to each struct object in the list to a unmanaged C++ Class through a Dll function call so it can be referred to during other function calls without the need to duplicate data on the unmanaged side. </p> <pre><code>class ProgramMain { public List&lt;Bin&gt; m_BinList; static void Main() { //Some functions calls //Fills up List&lt;Bin&gt; LoadBinData(string inFile); //Iterate each bin in list and pass reference to each bin to C++ class via //Dll Imported function PassPtrsToLibrary(); //??? } public void LoadBinData(string inFile) { ..... } public void PassPtrsToLibrary() { ???? } /* PassByReferenceIn */ [DllImport ("mylib")] public static extern void PassBinPtrIn(ref Bin theBin); //Some other function that reads the stored Bin pointers' data and perform calculations [DllImport ("mylib")] public static extern int ProcessBin(); } </code></pre> <p>On the C dll side, internally a global C++ class object stores the pointer to each struct in a std::vector container:</p> <pre><code>BinManager theBinManager; void PassBinPtrIn(Bin* theBin) { theBinManager.AddBin(theBin); } void BinManager::AddBin(Bin* theBin) { m_BinPtrList.push_back(theBin);//a std::vector&lt;Bin*&gt; type } </code></pre> <p>However I am facing some problems when writing the PassPtrsToLibrary() C# sharo function. After adding the Bin struct into the list, I can never get the actual pointer or reference to the bin inside the list. I have tried Marshall.StructureToPtr but it always crash my application. I also read that it is difficult to pass a managed string in struct as pointer/reference into C code. Please give me some help or advice as how to solve this problem. Thank you for reading this lengthy post.</p>
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