Custom Action type 50 has a very useful behavior. This custom action copies a value to a property. The cool thing about it is that you can copy any formatted string. That is, if you use , you can get the value of another property. and you can also use environment variables (with a % prefix), file paths (with a # prefix) and directory paths (with a $ prefix). So, to copy a property to another property, simply do this:
<CustomAction Id="CopyProperty" Property="TargetProperty" Value="[SourceProperty]" />
And then you’ll have two properties with the same value!