When to Call the Constructor of a Base Class.

You can use the base keyword in a constructor, to call the constructor of a class’ base class.  You’d most typically do this to allow the constructor in the base class to initialize the data members that are defined in the base class.  Then the constructor of the derived class can initialize its own data members.
Read more: http://csharp.2000things.com/2013/01/29/768-when-to-call-the-constructor-of-a-base-class/