Return new object in COM DLL.

[RYU]

Hi, I have created a new COM DLL and just wondering how to return a new COM object. Here is my code (in COM DLL) to return a new object.

HRESULT __stdcall CMainTestClass::GetSamTest(IAdd **ppRetVal)
{
    CAddClass *pAddClass = new CAddClass();
    *ppRetVal = pAddClass;
    return S_OK;
}

When I call this function in C#, it gave me this error:

The runtime has encountered a fatal error. The address of the error was at 0x7f628678, on thread 0x105c. The error code is 0xc0000005. This error may be a bug in the CLR or in the unsafe or non-verifiable portions of user code. Common sources of this bug include user marshaling errors for COM-interop or PInvoke, which may corrupt the stack.

My C# code:

    MyTestLib.MainTestClass oMainObject = new MyTestLib.MainTestClass();
    MyTestLib.AddClass addObject = (oMainObject .GetSamTest() as MyTestLib.AddClass );
    MessageBox.Show(addObject.DoTheAddition().ToString());    //it fails here

Thanks for any help :)