C++ COM CoCreateInstace() returns -858993460

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C++

C#

COM

DLL

I have a third party .NET dll which I want to expose to a native C++ dll, so I wrote a wrapper dll in C#; But in the native C++ dll, every time when it excutes to CoCreateInstance(), it returns this -858993460 erroe;

----------------------Below is the structure of the program-----------------

ThorDetectorSwitch.dll(native C++ dll) -> MCLWrapper.dll(COM C# dll) -> mcl_RF_Switch_Controller64.dll(third part .NET dll)

----------------------Below is some o my code-----------------------

The C# wrapper dll (MCLWrapper.dll, COM callable wrapper dll):

// C# COM wrapper for mcl_RF_Switch_Controller64.dll
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using mcl_RF_Switch_Controller64;
using System.Runtime.InteropServices;
// for function reference see miniCircuit RF controller manual

namespace MCLWrapper
{
    [Guid("727C569D-09AF-472c-8032-2AC9BC7CDC30")]
    [InterfaceType(ComInterfaceType.InterfaceIsDual)]
    [ComVisible(true)]
    public interface MCLControl
    {
        [DispId(1)]
        void Connect(string SerialNumber);

        [DispId(2)]
        void Set_Switch(string SwitchName, int Val);

        [DispId(3)]
        void Set_SwitchesPort(byte binVal);

        [DispId(4)]
        void GetSwitchesStatus(int statusRet);

        [DispId(5)]
        void Disconnect();
    };

    [Guid("68A7F8A1-6347-4bb1-9809-EE18E1E9BDD6")]
    [ClassInterface(ClassInterfaceType.None)]
    [ProgId("MCLWrapper.MCLControlClass")]
    public class MCLControlClass : MCLControl
    {
        public USB_RF_SwitchBox _sb = new USB_RF_SwitchBox();

        //public MCLControlClass() { }
        public void Connect(string SerialNumber)
        {
            _sb.Connect(ref SerialNumber);
        }

        public void Set_Switch(string SwitchName, int Val)
        {
            _sb.Set_Switch(ref SwitchName, ref Val);
        }

        public void Set_SwitchesPort(byte binVal)
        {
            _sb.Set_SwitchesPort(ref binVal);
        }

        public void GetSwitchesStatus(int statusRet)
        {
            _sb.GetSwitchesStatus(ref statusRet);
        }

        public void Disconnect()
        {
            _sb.Disconnect();
        }
    }
}

The constructor of ThorDetctorSwitch.dll (The native C++ that calls the CCW MCLWrapper.dll):

#import "../MCLWrapper/MCLWrapper/bin/Debug/MCLWrapper.tlb" raw_interfaces_only

using namespace MCLWrapper;

MCLWrapper::MCLControl *_mcSwitch;

ThorDetectorSwitch::ThorDetectorSwitch()
{
    HRESULT hr = CoInitialize(NULL);
    MCLWrapper::MCLControlPtr mclSmartPtr;
    hr = ::CoCreateInstance(__uuidof(MCLWrapper::MCLControlClass), NULL,CLSCTX_ALL, __uuidof(MCLWrapper::MCLControl), (void**)&mclSmartPtr    );
    _mcSwitch = mclSmartPtr;

    _A  = WstringToBSTR(L"A");
    _B  = WstringToBSTR(L"B");
    _C  = WstringToBSTR(L"C");
    _D  = WstringToBSTR(L"D");

    _deviceDetected = FALSE;
}

The command line I used to register MCLWrapper.dll

regasm MCLWrapper.dll /tlb:MCLWrapper.tlb /codebase

and it returns registry successfully.

Error:
The error occurs at

hr = ::CoCreateInstance(__uuidof(MCLWrapper::MCLControlClass), NULL,CLSCTX_ALL, __uuidof(MCLWrapper::MCLControl), (void**)&mclSmartPtr    );

and I don't think this line is completely excuted.

Anyone has any idea? Thanks a lot.