#692 – Two Approaches for Optional Parameters in Constructors

When you create an instance of an object, you may want to pass different combinations of parameters for purposes of initializing the object.  In authoring a class, there are a couple different ways to support this.

You can declare multiple constructors, each supporting a different set of parameters.  You can use constructor chaining to invoke the main constructor, to centralize object initialization.

        public Dog(string name, int age, string favToy )
        {
            // Do all parameter validation here
            Name = name;
            Age = age;
            FavoriteToy = favToy;
        }

        public Dog(string name) : this(name, 1, null)
        {
        }

        public Dog(string name, int age) : this(name, age, null)
        {
        }

        public Dog(string name, string favToy) : this(name, 1, favToy)
        {
        }

You can also use optional parameters in a single constructor, to do the same thing.

        public Dog(string name, int age = 1, string favToy = null)
        {
            // Do all parameter validation here
            Name = name;
            Age = age;
            FavoriteToy = favToy;
        }