Need approach for Setting value to a property based on various conditions

I have many properties spread across a number of classes. Value to these properties need to be assigned based on a number of conditions (around 5 to 8 for each property). I am looking for an alternative for numerous 'if else' conditions.

I have come across 'Rule Engine' off late but AFAIK it can be used for validating the rules.

Any Design suggestion would be of great help.