using System;

using System.Collections.Generic;

​

namespace Generics

{

    //non-generic classes

    public class IntegersList

    {

        public void Add(int item)

        {

            //...

        }

    }

​

    public class StringsList

    {

        public void Add(string item)

        {

            //...

        }

    }

​

    public class DoublesList

    {

        public void Add(double item)

        {

            //...

        }

    }

​

    //generic class

    public class List<T>

    {

        public void Add(T item)

        {

            //...

        }

    }

​

    #region constraints

​

    public class OnlyReferenceTypes<T> where T : class

    {

​

    }

​

    public class OnlyValueTypes<T> where T : struct

    {

​

    }

​

    public class OnlyTypesWithParameterlessConstructor<T> where T : new()

    {

​

    }

​

    public class BaseClass

    {

​

    }

​

    public class OnlyDerivedFromBaseClass<T> where T : BaseClass

    {

​

    }

​

    public interface IFlying

    {

​

    }

​

    public class OnlyImplementingIFlyingInterface<T> where T : IFlying

    {

​

    }

​

    #endregion

​

    public class Program

    {

        static void Main(string[] args)

        {

            var currencies = new Dictionary<string, string> 

            {

                ["USA"] = "USD",

                ["Great Britain"] = "GBP"

            };

​

            var yearsOfBirth = new Dictionary<string, int>

            {

                ["John Smith"] = 1980,

                ["Monica Smith"] = 1983

            };

​

            //var invalidObject = new OnlyImplementingIFlyingInterface<int>(); //will not compile as constraint is not met

            //Console.ReadKey();

        }

    }

}