How to Call CoGetClassObjectFromURL() in an MFC App (174653)
The information in this article applies to:
- Microsoft Visual C++, 32-bit Enterprise Edition 5.0
- Microsoft Visual C++, 32-bit Enterprise Edition 6.0
- Microsoft Visual C++, 32-bit Professional Edition 5.0
- Microsoft Visual C++, 32-bit Professional Edition 6.0
- Microsoft Visual C++, 32-bit Learning Edition 6.0
- Microsoft Internet Explorer (Programming) 4.0
- Microsoft Internet Explorer (Programming) 4.01
- Microsoft Windows Internet Services (WinInet)
This article was previously published under Q174653 SUMMARY This Urlobj.exe sample demonstrates how to call the
CoGetClassObjectFromURL() function to download, register, and instantiate an
object. The sample implements two interfaces necessary to allow the
CoGetClassObjectFromURL() function to work properly: IBindStatusCallback and
IWindowForBindingUI. MORE INFORMATIONThe
following files are available for download from the Microsoft Download
Center: Visual C++ 6.0 For
additional information about how to download Microsoft Support files, click the
following article number to view the article in the Microsoft Knowledge Base: 119591 How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most
current virus-detection software that was available on the date that the file
was posted. The file is stored on security-enhanced servers that help to
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Visual C++ .NET
Release Date: July 2, 2002
For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:
119591 How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file.
The CoGetClassObjectFromURL() function returns a class
factory object for a given CLSID. If the desired object is installed on the
system, it is instantiated. Otherwise, the necessary code is downloaded and
installed from the specified URL. The sample uses a CFormView to get the value
of the CLSID, the URL pointing to the code for the ActiveX object, the major
and minor version, and the size of the object for displaying (it assumes that
the control will display itself in some manner). The bulk of the
relevant code is found in the OnButton1() handler, which starts the download
process, and the OnStopBind() handler, which handles creating the object after
it has finished downloading. The IBindStatusCallback and
IWindowForBindingUI interfaces are implemented in the file Download.cpp by
using a CCmdTarget derived class and the MFC interface map macros.
After the CoGetClassObjectFromURL() has completed the asynchronous download,
the OnStopBind() handler is called to display the control. In this handler the
sample demonstrates instantiating the actual object by using the
CWnd::CreateControl() function. This is assuming that the object is an OLE
control. The handler also contains some code that has been commented out that
demonstrates calling IClassFactory::CreateInstance() in the case that the
object is not an OLE control. To maintain simplicity, the sample does
not implement much error checking or verification of user input.
| Modification Type: | Minor | Last Reviewed: | 8/5/2004 |
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| Keywords: | kbdownload kbfile KB174653 |
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