Automatically Notify Users about Program Updates

Using a Software Update Channel, you can automatically notify users when a new version of your program is available. This process is based on Open Software Distribution technology, and is sometimes known as "publishing."

Users can automatically be notified about a newer version of a program when they click a shortcut (.lnk file) to the program, such as a shortcut on the Start menu. To use this method to notify users, your program must enter version information into the registry. Internet Explorer can download the program when the channel subscription activates or when the user answers the prompt to update the software.

You can alter existing shortcuts to take advantage of this technology. Microsoft provides a utility, Blesslnk.exe, which can convert existing .lnk files into shortcuts that can use Software Update Channels. This utility will be available in the Internet Client SDK.

If the user's appropriate security zone (typically the Intranet zone) is set to Low security, you can use the <Precache> tag to automatically download the program. If you use the Precache tag, the user doesn't have to be connected to the Internet during installation.

Here is a sample channel that will notify the user about updates to the fictitious "Green" program. In this example, Green version "0,6,0,1" (6.1) is already installed on the computer, and a shortcut to Green exists on the Start menu.

The user has subscribed to a channel through the Channel Definition Format (.cdf) file shown below, with the exception that the version number is "0,6,0,1," the original version.

When Green is updated, a newer version of the program is made available at the location specified in the <Codebase> tag. The version number is updated as follows: (VERSION="0,6,0,2" ). The next time the user clicks the shortcut, the Software Update dialog box is shown, prompting the user to open a Web page that describes the new version of the program. The user can install the newer version from this Web page.

GREEN.CDF

<?XML version="1.0"?>
<!DOCTYPE Channel SYSTEM "http://www.w3c.org/Channel.dtd">

<CHANNEL HREF="http://testserver/logo5/logo5.htm">
	<TITLE>Green (MSAppLogo5) Test Channel</TITLE>
	<LOGO HREF="http://testserver/logo5/green.ico" STYLE="icon"/>
	<USAGE VALUE="SoftwareUpdate"/>
	<SOFTPKG HREF="http://testserver/logo5/logo5.htm"
		NAME="{55272F7E-1B37-11D1-8933-00805F8A4D63}"
		VERSION="0,6,0,2"
		STYLE="MSAppLogo5"
		PRECACHE="yes"> 
		<TITLE>Green</TITLE>
		<ABSTRACT>Abstract: Green v2.0 application installed via channel</ABSTRACT>
		<IMPLEMENTATION>
			<CODEBASE HREF="http://testserver/logo5/green-x.exe">
		</IMPLEMENTATION>
	</SOFTPKG>
</CHANNEL>