Re: Interface method vs QueryInterface()

"H Xia" <>
19 Dec 2006 07:45:22 -0800
It works. Thank you.

I don't understand why:

1). With the interface I got by CoCreateInstanceEx, I can call the
interface method; but not QueryInterface method (for any interface)?
Why I have to start from IUnknown?
2). For each interface I have to set proxy blanket to query other
interface, but this time I don't have to start from IUnknown.

On Dec 15, 12:54 pm, "Alexander Nickolov" <> wrote:

QI for IUnknown and set the proxy blanket on the returned
interface pointer.

Alexander Nickolov
Microsoft MVP [VC], MCSD

"H Xia" <> wrote in

What's difference between normal interface method and QueryInterface

In client side, I created an instance by calling:

  MULTI_QI qi = {&IID_ITestCP, NULL, S_OK};
  HRESULT hResult = ::CoCreateInstanceEx( CLSID_TestCP
                                        , NULL
                                        , CLSCTX_LOCAL_SERVER |
                                        , &serverInfo
                                        , 1
                                        , &qi

It created an instance and returned an interface from the instance.
Then I call the interface method after properly setting its Proxy
blanket, it succeeded. Then I go even further to query another
interface through the gotten interface, it failed.

  hResult = pUnk->BlanketInfo();
  hResult = pUnk->QueryInterface(IID_IConnectionPointContainer,
(void**)&pCPC); // access denied

My question is if the second call failed with access denied, why not
the first one?

Thanks in advance.

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