How to use IDispatch in plain C to call a COM object

activexccomgccidispatch

I need to compile some code of mine using the gcc compiler included in the R tools (R the statistical program for windows), the problem is that I need to use IDispatch in my code to create an access the methods of a COM object, and the gcc compiler doesn't support much of the code that I'm using to do so, which is basically C++ code.

So my question is how can I use IDispatch in C to create the COM object without having to depend on MFC, .NET, C#, WTL, or ATL. I believe that if I do so I will be able to compile my code without any problem.

Best Answer

There is a great article on CodeProject entitled "COM in plain C".

Here is the link to Part 1.

There is a lot of very good info on working with COM in C in that article and the author's subsequent follow-ups (I think there are 3 or 4 in the series).

Edit:
I was wrong, there are 8 parts!

Part 2
Part 3
Part 4
Part 5
Part 6
Part 7
Part 8

Related Solutions

C++ – Use of CoGetClassObject() in C – access COM Object interface

Here is a simple example in plain C++:

CoInitialize(NULL); // absolutely essential: initialize the COM subsystem
IMyInterface* pIFace;
// create the object and obtain a pointer to the sought interface
CoCreateInstance(CLSID_MyObject, NULL, CLSCTX_ALL, IID_IMyInterface, &pIFace);
pIFace->MethodIReallyNeed(); // use the object
pIFace->Release(); // free the object
CoUninitialize(); // cleanup COM after you're done using its services

Copied from here: COM Basics

C# – .NET2.0 C# Interop: How to call COM code from C#

Update: Based on question updates, I have removed the portions of my answer that are no longer relevant to the question. However, in case other readers are looking for a quick and dirty way to generate HTML in a winforms app and do not require an in-process IE, I will leave the following:

Possible Scenario 1: The ultimate goal is to simply display HTML to your end user and are using Windows Forms

System.Windows.Forms.WebBrowser is the painstakingly easy .NET wrapper for the interface you are trying to manually implement. To get it, Drag and drop an instance of that object from your toolbar (listed as "Web Browser" under the "All Windows Forms" section) onto your form. Then, on some suitable event handler:

webBrowser1.Navigate("about:blank");
webBrowser1.Document.Write("<html><body>Hello World</body></html>");

On my test app, this correctly displayed the haunting message we all have learned to fear and loath.

Best Answer

Related Solutions

C++ – Use of CoGetClassObject() in C – access COM Object interface

C# – .NET2.0 C# Interop: How to call COM code from C#

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