C++宿主程序如何通过注册表加载COM插件？

Question

契约接口：IDTExtensibility2
插件：实现了IDTExtensibility2接口

问题1：如何做一个C++宿主程序，加载该插件?

问题2：在CoCreateInstance时，返回no support such interface，但是注册表中有插件CLSID，也有接口的CLSID。

契约接口：ATL项目-ATLProject1
定义.idl接口，代码片段如下

[
    object,
    uuid(BB5F5302-CAD2-4A1C-B701-D4C127B2563F),
    dual,
    nonextensible,
    pointer_default(unique)
]
interface IDTExtensibility2 : IDispatch{
    [id(1)] HRESULT OnConnection([in] IDispatch* application, [in] enum ext_ConnectMode ConnectMode, [in] IDispatch* AddInInst, [in] SAFEARRAY(BSTR)* custom);
};

插件：C#类库-ClassLibrary1
引入ATLProject生成的COM库，实现IDTExtensibility2接口，代码片段如下

using ATLProject1Lib;
namespace ClassLibrary1
{
    public class Class1 : IDTExtensibility2
    {
        public Class1() { }

        public void OnConnection(object Application, ext_ConnectMode ConnectMode, object AddInInst, ref Array custom)
        {
            MessageBox.Show("OnConnection");
        }
    }
}

宿主：C++项目-
代码片段如下

#include "..\ATLProject1\ATLProject1_i.c"
#include "..\ATLProject1\ATLProject1_i.h"_
int _tmain(int argc, _TCHAR* argv[])
{
    CoInitialize(NULL);
    CLSID clsid;
    HRESULT hResult = CLSIDFromProgID(OLESTR("ClassLibrary1.Class1"), &clsid);
        CComPtr<IDTExtensibility2> pFirstClass;//智能指针
        hResult = CoCreateInstance(clsid, NULL, CLSCTX_INPROC_SERVER, IID_IDTExtensibility2, (void**)&pFirstClass);
            IDispatch* application = NULL;
            enum ext_ConnectMode ConnectMode = ext_cm_AfterStartup;
            IDispatch* AddInInst = NULL;
            SAFEARRAY** custom = NULL;
            hResult = pFirstClass->OnConnection(application, ConnectMode, AddInInst, custom);
        pFirstClass.Release();      
      CoUninitialize();

    return 0;
    }

Answer 1

CoCreateInstance+QueryInterface……然后你的插件往宿主那里查询什么接口你就得实现什么接口。