C#. How to silently uninstall software components packaged as EXEs?

We have a requirement wherein we need to be able to perform silent installation / uninstallation of software components packaged as EXEs.

We were able to perform silent installation using WMI.

However, we are running into trouble while trying to implement the uninstallation functionality. 
The articles that we have seen so far recomment using the "UninstallationString".
Some of the softwares that we install do not have this entry in the registryy. 
How can we perform the uninstallation in such scenarios?