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POSystem.Access Violation Exception While calling C++ Dll in .Net Application
 

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  1. POSystem.Access Violation Exception While calling C++ Dll in .Net Application
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    <p>I am implementing C++ Dll in the C#.</p> <p>My Wrapper.h file:</p> <p>`</p> <pre><code> class __declspec(dllexport) TestClass { public: int value; TestClass(int value):value(value) { } ~TestClass() { } } </code></pre> <p>`</p> <p>My Wrapper.cpp File</p> <pre><code> #include "stdafx.h" #include "WrapperApplication.h" </code></pre> <p>My C# code</p> <pre><code> public unsafe class Message:IDisposable { private TestStruct* _testStruct; private IntPtr* _oldVTable; [DllImport(@"WrapperApplication.dll", EntryPoint = "??0TestClass@WrapperApplication@@QAE@H@Z", CallingConvention = CallingConvention.ThisCall)] extern static IntPtr Test(TestStruct* testStruct, int value); public Message(int value) { _testStruct=(TestStruct*)Memory.Alloc(sizeof(TestStruct)); Test(_testStruct, value); } #region IDisposable Members public void Dispose() { //throw new NotImplementedException(); } #endregion } </code></pre> <p>My TestStruct.cs file:</p> <pre><code> [StructLayout(LayoutKind.Sequential, Pack = 4)] public unsafe struct TestStruct { public IntPtr* vtable; public int value; } </code></pre> <p>I have to Call CPP dll with the help of the <strong>Vtable</strong> in the .Net Application. I have created TestStruct.cs file as replica of My Cpp class. And trying to Call the CPP constructor in the C# constructor. But at the line <strong>Test(_testStruct, value);</strong> throws the System.AccessViolation Exception as Attempted to read or Write the memory.It is often indication that other memory is corrupt. The values for _teststruct, value in the Test ctor comes but still it throws the Exception.I have tried many ways but failed to get the solution. Please let me know where I am wrong in the implementaion. So Any Help would Appreciated.</p>
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    1. USSkoolBoyAtWork
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    1. COTest is the CPP constructor name which i am exported in the C#.
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      1. USSkoolBoyAtWork
    2. CO(oops, how silly of me) WAIT, your class as it is declared doesn't *have* a vtable, since it has no virtual functions. However, that's not a reason for the constructor call to cause an access violation.
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    3. COYes.I have to call C++ Dll in the C# by using Vtables and I know it needs some Virtual functions in the CPP Class... but at constructor it throws the Access Violation Exception
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      1. USSkoolBoyAtWork
 

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