Microsoft KB Archive/174653

Knowledge Base

How to Call CoGetClassObjectFromURL() in an MFC App

Article ID: 174653

Article Last Modified on 8/5/2004

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APPLIES TO

• Microsoft Visual C++ 5.0 Enterprise Edition
• Microsoft Visual C++ 6.0 Enterprise Edition
• Microsoft Visual C++ 5.0 Professional Edition
• Microsoft Visual C++ 6.0 Professional Edition
• Microsoft Visual C++ 6.0 Standard Edition
• Microsoft Internet Explorer 4.0 128-Bit Edition
• Microsoft Internet Explorer 4.01 Service Pack 2
• Microsoft Windows Internet Services (WinInet)

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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 INFORMATION

The following files are available for download from the Microsoft Download Center:

Visual C++ 6.0

Download Urlobj.exe now

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.

Visual C++ .NET

Download Urlobjvcnet.exe now

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.

Additional query words: softlib

Keywords: kbdownload kbfile KB174653

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