I have been using ClickOnce to install and update mysoftware for the past few years. I decided to switch installers to NSIS. It isn't feasible for individual users of the software to uninstall the software and then re-install(with the NSIS installer).
I thought about adding some code in my NSIS script to delete the registry key for the application before installing the software but Microsoft highly recommends to use the Windows Installer service for uninstalls.
My questions are 1.What is the danger of installing without uninstalling the previous version? and 2.is there a way(using NSIS or through another means) to programatically uninstall the previously installed version before installing the current version?
The typical consequence of not removing the per-user click once installation(s) is that the user might be confused by two versions of the program. For example this could be two different office addins active.
I did some searching on the silent uninstall question and I'm not sure if ClickOnce ever supported this or not. I did find some open source projects that reported to being able to do this. Implementing them into an ActiveSetup style pattern to get it to run in each user context would seem to handle getting rid of the old versions.