A little example of generics and how they might be used.

GenericsExample1.cs

using System;
using System.Linq;
using System.Collections.Generic;

namespace Generics
{
	/// <summary>
	/// We use the interface to describe how an animal should be behave, anything that is an IAnimal has to conform to these specs
	/// </summary>
	public interface IAnimal
	{
		void Walk();
		void Eat();
		void Drink();
		string Name { get; }
	}

	/// <summary>
	/// Dog is an IAnimal
	/// </summary>
	public class Dog : IAnimal
	{
		string name;

		public Dog(string name)
		{
			this.name = name;
		}

		public string Name { get { return name; }}

		public void Drink()
		{
		}

		public void Eat()
		{
		}

		public void Walk()
		{
		}
	}

	/// <summary>
	/// Cat is an IAnimal
	/// </summary>
	public class Cat : IAnimal
	{
		string name;

		public Cat(string name)
		{
			this.name = name;
		}

		public string Name { get { return name; } }

		public void Drink()
		{
		}

		public void Eat()
		{
		}

		public void Walk()
		{
		}
	}

	public class FunWithAnimals
	{
		/// <summary>
		/// An Example of being able to use both Cats and Dogs together because they both confirm to the IAnimal interface
		/// </summary>
		/// <returns>The and dogs.</returns>
		public IList<IAnimal> CatsAndDogs()
		{
			return new List<IAnimal>()
			{
				new Dog("Hoochy"), new Dog("Spot"), new Cat("Puffles")
			};
		}

		/// <summary>
		/// Gets the name of an IAnimal, where we say T, we mean an object, the where bit at the end of the method is  
		/// called the Generic Constraint, it's where we say whatever object we put in the place of T must be an IAnimal
		/// </summary>
		/// <returns>The name.</returns>
		/// <param name="animal">Animal.</param>
		/// <typeparam name="T">The 1st type parameter.</typeparam>
		public string SayHelloToAnimal<T>(T animal) where T : IAnimal
		{
			return "Hello " + animal.Name;
		}


		/// <summary>
		/// Put together the methods above, first we get a list of cats and dogs, then we use the Linq, select extension method and 
		/// call SayHelloToAnimal on each one... We can  treat them all as IAnimals and be guarenteed that we get a name off each one
		/// </summary>
		/// <returns>The of cats and dogs.</returns>
		public IEnumerable<string> NamesOfCatsAndDogs()
		{
			return this.CatsAndDogs().Select(animal => this.SayHelloToAnimal(animal));
		}


	}
}