Using .NET component in C++ code

Referring a C++ COM component is easy in .NET; all we have to do is to

• register (regsvr32 <dll_name_with_full_path>)
• Add a reference to the COM dll in the Visual Studio Solution
• An Interop file will be created in the bin directory of .NET project and we are done 

But the reverse is not as simple as above.

So this time I have come up with Steps we need to follow in order to refer a COM visible .NET dll in C++ code. 

 

• Register the COM Visible .NET assambly with regasm like this:

regasm <dll_name_with_full_path> /tlb

e.g. regasm "C:\SampleProject\bin\Release\Atreya.Anugrah.ComVisibleComponent.dll" /tlb

• Refer .NET component in .h file like this:

#import "<generated_tlb_name_with_full_path>" named_guids raw_interfaces_only

e.g. #import "C:\SampleProject\bin\Release\Atreya.Anugrah.ComVisibleComponent.tlb" named_guids raw_interfaces_only 

• Create a class in .h file, and declare member variable like this:

ComVisibleComponent::<Name_of_Interface>* memberVariablePointer;

e.g. Atreya_Anugrah_ComVisibleComponent::IMyInterface* m_pIMyInterface; 

• Now, Initialize the declared member variable pointer in .cpp file like this: 

hr = CoCreateInstance( __uuidof(Atreya_Anugrah_ComVisibleComponent::<Name_of_CoClass_Implementing_Interface>),          // COM class id

                                        NULL,                                                                                                                                                  // Outer unknown

                                        CLSCTX_ALL,                                                                                                                                       // Server INFO

                                        Atreya_Anugrah_ComVisibleComponent::IID_<Name_of_Interface>,                                                // interface id

                                        (void**) &m_pIMyInterface   );                                                                                                                 // Returned Interface 

if (FAILED(hr))

{

       _com_error e(hr);

   strErrorMsg.Format("Error: Unable to create COM Visible .NET component. hr = %d. Message = %s",hr, e.ErrorMessage());

   return hr;

}

          //you are good to use your initialized pointer here :)   

     m_pIMyInterface->foo()

 

P.S. This post does not explain that how can we make our .NET component as COM visible. Please refer other post/article for that as it is quite simple activity.

    

Namaste (Thanks and Regards)

| Anugrah Atreya