#1,138 – Type Parameters in Generic Methods Can Be Constrained

You can constrain the type parameters in a generic class in a number of different ways.  You can also constrain type parameters in generic methods, using the same types of constraints.

In the example below, we define a generic method Bury<T> in the Dog class.  We constrain the type parameter, indicating that it should implement the IBuryable interface.

    public class Dog
    {
        public string Name { get; set; }

        public Dog(string name)
        {
            Name = name;
        }

        // Generic method
        public void Bury<T>(T thing) where T: IBuryable
        {
            Console.WriteLine("{0} is burying: {1}", Name, thing);
        }
    }

We can pass the Bury method any object that implements IBuryable.

            Dog d = new Dog("Bowser");
            d.Bury(new Bone());

If we try passing an object that does not implement IBuryable, we’ll get a compile-time error, indicating that the compiler can’t convert to IBuryable.