I am trying to suppress the process of removing existing product while upgrading. I am using the following code:
<RemoveExistingProducts Suppress='yes'></RemoveExistingProducts>
It throws an error saying: Please stop overriding the base definition
You may be misunderstanding what an upgrade is - this seems to be a fairly common misconception.
A major upgrade (RemovePreviousVersions) is not a patch, or hotfix or anything you might think of as updating the files in the currently installed product. A major upgrade is a complete product install of a full working product that happens to include removal of an earlier version if there is one installed. Requirements to perform a major upgrade include having a higher product version and a different product code.
On the other hand if you want to install two "copies" of the same product, then simply don't use a major upgrade, and change your product code (and package code). You'll get two copies of the same product installed, and whether that all works depends among other things on whether the two copies of the application play well together and whether you can uninstall one without damaging the other.
Why do you want to suppress the upgrade? RemoveExistingProducts is a central part of implementing a Windows Installer major upgrade - the standard way to upgrade to higher versions of your application - for example from version 1.0 till 2.0. The RemoveExistingProducts action will remove or check for the existence of an existing version on the system based on the settings in the Upgrade table. You can author this table to uninstall any MSI file you want, and you can add entries that check if certain packages are installed and then aborts with a warning to the user that a previous version is installed - usually this is used to make lower version setups aware of higher versions installed and then aborting.
More on upgrades via Wix here: http://wix.tramontana.co.hu/tutorial/upgrades-and-modularization.
And perhaps quickly check these "Wix quick start" recommendations: MSI vs nuget packages: which are is better for continuous delivery?
