In C# it is not possible to call another constructor from inside the method body. You can call a base constructor this way: foo(args):base() as pointed out yourself. You can also call another constructor in the same class: foo(args):this().
When you want to do something before calling a base constructor, it seems the construction of the base is class is dependant of some external things. If so, you should through arguments of the base constructor, not by setting properties of the base class or something like that