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POHow to add new functions to a COM .dll created by a Visual Studio C++ ATL Project
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  1. POHow to add new functions to a COM .dll created by a Visual Studio C++ ATL Project
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    copied!<p>I'm trying to create a very basic COM dll for inclusion in a C# project, to then use to wrap up some C++ functionality into a COM module for inclusion in a C# project (the language used by the rest of the code base).</p> <p>I included the COM dll, added a class to the COM dll and instantiated it in the C# code, but so far I haven't been able to add new functionality to the new class.</p> <p>Here's what I did: </p> <ol> <li>New Visual C# Windows Forms Application </li> <li>Right click solution->Add->New Project... </li> <li>Add New Visual C++ ATL Project (called MyCOMDLL) </li> <li>Default options chosen in ATL Project Wizard (I've also tried ticking 'Support COM+ 1.0')</li> <li>Right click MyCOMDLL project->Add->Class </li> <li>Add New Visual C++ ATL COM+ 1.0 Component </li> <li>Typed 'MyCOMObject' into Short name, which automatically populated the other fields in the 'Names' tab </li> <li>Left the other settings as default </li> <li>Built the MyCOMDLL project</li> <li>Add a reference to the new MyCOMDLL.dll to the C# Windows Forms Application <li>Right Click C# Windows Forms Application Project->Properties <li>On the Build tab set Platform target to x86 <li>Add "using MyCOMDLLLib;" to Form1.cs file <li>Add a button to the Form and in the button click function add</li> </ol> <p><pre><code>MyCOMDLLLib.MyCOMObjectClass myVariable = new MyCOMObjectClass();</pre></code></p> <p>I've tried various things so won't list any except the most obvious here - I tried adding a class method to MyCOMObject.h:</p> <p><pre><code>// CMyCOMObject class ATL_NO_VTABLE CMyCOMObject : public CComObjectRootEx, public CComCoClass, public IDispatchImpl { public: CMyCOMObject() { }</p> <pre><code>DECLARE_PROTECT_FINAL_CONSTRUCT() HRESULT FinalConstruct() { return S_OK; } void FinalRelease() { } </code></pre> <p>DECLARE_REGISTRY_RESOURCEID(IDR_MYCOMOBJECT)</p> <p>DECLARE_NOT_AGGREGATABLE(CMyCOMObject)</p> <p>BEGIN_COM_MAP(CMyCOMObject) COM_INTERFACE_ENTRY(IMyCOMObject) COM_INTERFACE_ENTRY(IDispatch) END_COM_MAP()</p> <p>// IMyCOMObject public: // SB: My attempt at adding a new method int ReturnTwo() { return 2; } };</pre></code></p> <p>The ReturnTwo method was visible in the class view of CMyCOMObject, but not visible in the class view of MyCOMObjectClass in the C# Windows Forms Application project. </p> <p>Any help much appreciated.</p>
 

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