Why is it necessary for a base class to have a constructor that takes 0 args?

Question

This won\'t compile:

namespace Constructor0Args
{
    class Base
    {
        public Base(int x)
        {
        }
    }

    class Derived : Base
    {
    }         


        

Answer 1

When you derive a class from another, the base class will be called before the derived classes constructor. When you don't explicitly call a constructor you are essentially writing

class Derived : Base
{
    public Derived() : base()
    {
    }
}

Since the Base class doesn't have a 0 argument constructor, this is invalid.