In the Condition tabpage you will see all the Conditions that are used in the script. 

 

Adding a new Condition

And check the installed .NET version:

 

  • Set a check at the .NET version that is required by the installer.
    SetCondition2

 

  • For this to work you need to add the reference WixNetFxExtension to the Visual Studio project, in visual studio you can select add reference in the menu.
    AddReferences WixNetFxExtention