I have multiple projects in a solution. Each project has its own `app.config` file. I want to have a single `app.config` or settings file which can be used across the solution. What I see is now, when i want to add some settings common to the application I will have to add an entry it in all the projects `app.config` file.

I want to have a single configurable file (XML) which can be used in whole application. At run time if the value of any key is changed, my application should be able to get that changed value from the XML.