Understanding Extension Methods and Mixin

using System;
using System.Collections.Generic;

/* contact:
 * abhijit.gadkari@gmail.com
 * 
 * */

namespace ExtensionMethods
{
    interface IPerson
    {
        int age { get; set; }
        String name { get; set; }
    }

    class Person : IPerson
    {
        private int _age;
        private string _name;

        #region IPerson Members

        public int age
        {
            get
            {
                return _age;
            }
            set
            {
                if (value > 0)
                {
                    _age = value;
                }

            }
        }

        public string name
        {
            get
            {
                return _name;
            }
            set
            {
                if (!string.IsNullOrEmpty(value))
                {
                    _name = value;
                }
                else
                {
                    _name = "Unknown";
                }
            }
        }

        #endregion
    }

    static class ExtendIPerson
    {
        public static bool CanDrive(this IPerson testPerson, bool isDriver)
        {
            return isDriver;
        }
    }

    public static class ExtensionMethods
    {
        public static bool IsGreaterThanZero(this int Number)
        {
            return Number > 0 ? true : false;
        }
    }

    public class City
    {
        private string _name;
        private string _state;

        public City(string name, string state)
        {
            this._name = name;
            this._state = state;
        }

        public string Name
        {
            get
            {
                return _name;
            }
        }


        public string State
        {
            get
            {
                return _state;
            }
        }
    }

    public static class ExtendCity
    {

        public static bool IsCityinCalifornia(this City c)
        {
            return c.State == "CA" ? true : false;
        }
    }

    class Program
    {
        static bool StaticIsGreaterThanZero(int Number)
        {
            return Number > 0 ? true : false;
        }

        static void Main(string[] args)
        {
            #region Simple IF logic

            int NumOne = 10;

            if (NumOne > 0)
                Console.WriteLine("Number : {0} is greater than 0", NumOne);

            #endregion

            #region decouple IF logic into a seperate static method

            if (StaticIsGreaterThanZero(NumOne))
            {
                Console.WriteLine("Number : {0} is greater than 0", NumOne);
            }

            #endregion

            #region Extension method implementation

            if (NumOne.IsGreaterThanZero())
            {
                Console.WriteLine("Number : {0} is greater than 0", NumOne);
            }

            #endregion

            #region Extending the custom type

            City c = new City("Santa Ana", "CA");
            City c1 = new City("Bloomington", "IN");

            List<City> cities = new List<City>();

            cities.Add(c);
            cities.Add(c1);

            foreach (City _city in cities)
            {
                //IsCityinCalifornia() is an extension method
                if (_city.IsCityinCalifornia())
                {
                    Console.WriteLine("City Name : {0} and City State : {1}", _city.Name, _city.State);
                }
            }

            #endregion

            #region Mixin Implementation

            IPerson ip = new Person();

            ip.name = "ABC";
            ip.age = 21;

            if (ip.CanDrive(true))
            {
                Console.WriteLine(ip.name + " can drive");
            }

            #endregion

            Console.ReadLine();
        }
    }
}