How to force an application to use .NET 3.5 or above?

Question

Our application is built with VS 2008, uses Linq and has Target Framework set to .NET Framework3.5.

It works OK when only .NET 3.5 or 4 is installed on the machine.<

Answer 1

Forming the question led me to the answer. As mentioned in the Element documentation,

When multiple versions of the runtime are supported, the first element should specify the most preferred version of the runtime, and the last element should specify the least preferred version.

So the way to achieve the second option ("CLR 4 if it is installed, and CLR 2 is CLR 4 is not installed") is to reverse the order of the elements in app.config:

This way, .NET 4 will be loaded if it is installed, and an earlier version will be loaded if not.