Windows Installer - force users to remove via Add?remove Programs

We have an installer solution written in Visual Studio 2005 Installer; that calls a C# custom action and we have hit a known issue, regarding the fact that on an upgrade - the old install code is run and not the new code, because Windows is running a ca开发者_运维知识库ched version of the custom action dll. We know this and although not over the moon about it - we have moved on.

When we release a new version of the installer and a user runs it, we now want it to check to see if an ealier version is installed - if there is one; we want to display a message telling them that they have to remove the old version via Add/Remove Programs. We know if they do a manual uninstall followed by an install, then all is fine and dandy - BUT it doesn't matter how many times we tell our users, via documentation; that this is what they have to do - they will still try and just run the new installer, without removing the old version first.

Therefore, we would like to put up a message and thus force them to to what they are told !! I've seen some installers do this ( though of course not sure what installer package was used to create these ). We only have VS 2005 and of course orca !!

Cheers,

Chris.

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This can be done through a custom launch condition:

• create a search which determines if the old version is installed (you can search for a component, registry entry or file)
• use the search property as a custom launch condition

For example, if the search property is OLD_VERSION, the launch condition can look like this:

Condition: NOT OLD_VERSION

Description: An older version was found. Please uninstall it using "Programs and Features" in Control Panel.

When OLD_VERSION property is set to a value (an older version is found), this launch condition will show the message and stop the install process.

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This doesn't quite make sense. Have you remembered to change the package GUID in your new setup? The package GUID identifies a specific setup file, and if two MSI files have identical GUID they will be treated as the same file regardless of whether they are or not. This could trigger a cached version of the MSI to be invoked and all sorts of hell breaks loose.

I would recommend reading up on "major upgrades" which will allow automatic uninstall of the existing version before the new version is installed. You also need to make sure you understand the basics of the technology before deploying to the wild. You must NEVER use identical package GUIDs for any MSI files. It's practically always wrong, and will lead to very mysterious problems.

I can't write up the whole major upgrade solution here, but basically it involves authoring the "Upgrade" table of your MSI to detect versions to uninstall. You need to change the package code, product code and version number (only 3 digits matter) and keep the same upgrade code (two MSI files with the same upgrade code "know" they are related - i.e they are from the same product family). Check MSDN for samples of major upgrades.

NB! If you have deployed MSI files with duplicate package GUIDs to your developer machine, it could have stray installs that must be cleaned up with MSIZap or similar. Use caution, or better yet test your new installer on a clean test system. Developer systems are full of junk and not generally good for MSI testing.