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I am working in a project in that i have a native(c++) application and a COM DLL(c# .Net). My requirement is, form my native application I want to call a function in COM DLL, and that function returns string(out parameter).

Bellow is the code

C# COM Code....

[ComVisible(true)]
public interface IUserDetais
{
    bool GetUserConfigData(out string configData);
}

[
ComVisible(true),
ClassInterface(ClassInterfaceType.None),
GuidAttribute("GUID"),
]
public class AppUserDetais : IUserDetais
{
    public bool GetUserConfigData(out string configData)
    {
        configData = "Some JSON content.";
        reurn true;
    }
}

C++ code

void GetUserInfo(IUserDetais* pUserInfo)
{
    // TODO, How to call the function. what should be the signature in C#(the out string length can vary and how to delete the memory allocated).
    //pUserInfo->GetUserConfigData();
}

Can any one tell me how to to call GetUserConfigData in C++ code.

Updated:

C++ is not .Net code. it is C++ win32 or native code.

Improve this question
4
  • Check this - stackoverflow.com/questions/186477/… Commented Nov 4, 2015 at 9:37
  • Do let IntelliSense help you to fall into the pit of success, it tells you a lot about how to call this method properly. You need two arguments, a BSTR* and a VARIANT_BOOL*. Don't forget to check the HRESULT return value and SysFreeString() to release the string. Commented Nov 4, 2015 at 10:05
  • Modify definition as GetUserConfigData([Runtime::InteropServices::Out] string^% configData) Commented Nov 4, 2015 at 10:24
  • You have asked the wrong question. You are not trying to call managed code from unmanaged code. You are trying to access a language-neutral COM object from a programming language, that can consume COM interfaces. The answer to this question is very different from the answer to the question you asked. Commented Nov 5, 2015 at 13:27
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