Partial classes in C#

Partial Classes in C#--> Partially define some methods in one file , add new methods to a class in another file, as shown below. it can be applied to class, struct or interface.

keyword: partial

file1.cs

namespace ConsoleApplication5
{
    public partial class Person
    {
        int Age;
        string Name;
        public Person(int age, string n)
        {
            Age = age;
            Name = n;
        }

        public bool isEligible() { if (Age > 18) return true; else return false; }
    }
}

file2.cs

namespace ConsoleApplication5

{

     public partial class Person

    {

         int pin;

         public Person(int p)

         {

             pin = p;

         }

         public bool isPinValid()

         {

             if (pin >100000 && pin > 999999) return false;

             else return true;

         }

     }

}

Program.cs(application Main file)

namespace ConsoleApplication5

{

    class Program

    {

        static void Main(string[] args)

        {

            Person p = new Person(20,"sitapati");

            Console.WriteLine(p.isEligible());

        }

    }

}