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Questions tagged [queryinterface]

31 questions
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votes
3 answers

Delphi: How to implement QueryInterface of IUnknown?

In Delphi, IUnknown is declared as: function QueryInterface(const IID: TGUID; out Obj): HResult; stdcall; Note: The output parameter is untyped In my TInterfacedObject descendant i need to handle QueryInterface, so i can return an object that…
Ian Boyd
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4 answers

How to get the id (memory address) of dll-function?

I want to use a function from nvapi in C# "NvAPI_DRS_EnumProfiles". I have to call QueryInterface(id) with the id of the function. Everything is working fine and i found the ids for the other functions i need on the web, but i can't find the id of…
MaxPower
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Why is every successful QueryInterface() call followed by Release() call?

Why is a QueryInterface() call always followed by a Release() call? For example, I have seen a sample code from MSDN as below: HRESULT hr = S_OK; CDecoder *pObj = new CDecoder(&hr); if (SUCCEEDED(hr)) { *ppv = NULL; hr =…
Arun Reddy Kandoor
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3 answers

How do Powershell query interface on a COM object

I created a COM object using Powershell: $obj = new-object -com MyLib.MyObj Then I need to query the interface "MyLib.MyInterface" on that object, but I have no idea how to do it with PowerShell. In other words suppose I have the below C++…
Shuping
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4 answers

Does IUnknown::QueryInterface() increment the reference count?

If I have an IUnknown *ptr, do I need to call Release() on every interface I obtain through ptr->QueryInterface(), in addition to calling ptr->Release() when I'm done with ptr? I used to think that the answer is "Yes", but this quote from MSDN…
user541686
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What is IconnectionPoint and EventHandling

Trying to understand What is IConnectionPoint and how this is connected to IConnectionPointContainer,IEnumConnectionPoints,IEnumConnections and EventHandling. Read the artcicles from MSDN and CodeProject which is explaining a about other methods…
Simsons
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InvalidCastException, QueryInterface call failing on COM component

I'm trying to use PCAnywhere's Ole automation in a .net applicaction I'm currently developing (VS 2010, c#). PCA 12.5 comes with a couple tlb files that when I try to add as references through VS I get an error on both saying 'A reference to…
rhyek
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Handling CoCreateInstance return value

Here's a code sample creating a COM object: CComPtr pFilter; auto hr = CoCreateInstance(CLSID_DMOWrapperFilter, NULL, CLSCTX_INPROC_SERVER, IID_IBaseFilter, reinterpret_cast(&pFilter)); I've seen somewhere that checking if…
Dalamber
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Access violation casting IDispatch in XE2

We're using some old code (ComLib.pas created by Binh Ly) so we can use the enumeration interface on an (OleVariant) object: type TDispNewEnum = dispinterface ['{97079E31-6957-11D2-9154-0000B4552A26}'] // dummy property _NewEnum: IUnknown…
Mick
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How can I do a Custom QueryInterface for .NET 3.5?

I have .NET Assembly exposed to COM, and I want to create a custom QueryInterface, otherwise my Class will have to implement a lot of interfaces. Currently my implementation is like…
Pablo Retyk
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Porting comtypes to win32com

In a Python script I have to replace usage of comtypes by win32com and pythoncom. Essentially I have this code: from comtypes.client import CreateObject, GetEvents object_IXXObjManager = comtypes.client.CreateObject(xxxId) connection_IXXObjManager…
skotka
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Get IID from interface name in C++? (VS 2010 automation)

Given the name of a COM interface as a string, how do I get the corresponding IID so that I can call QueryInterface()? For example: // Attempt to cast IDispatch referenced by pDisp to an ICommandBarButton char *interface_name =…
Chungzuwalla
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E_NOINTERFACE while trying to get a class method pointer

I'm calling the C# methods from a C++ unmanaged code. I have a problem with getting a value from a class instance returned in array. I've simplified the code a little bit This is the problematic method. [return:…
Mirek
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C# - object casting

As far as I know, if we're dealing with COM interfaces, any simple cast will usually trigger the QueryInterface routine, which is used to determine if the object actually implements the corresponding COM interface. object whatever; IComInterface…
Yippie-Ki-Yay
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Using the RFCOMAPIlib (RightFax COM API): Unable to cast COM object

I'm working with the RightFax COM API. What I want to do is simply send a fax with an attachment. Simple right? That question has been answered a few times. However, when I use some of that code in my application, I have a little…
Erik
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