Event & EXTENSION METHODS

        
        
        
        
    
protected void Page_Load(object sender, EventArgs e)
        {
            Button objC = new Button();
        }

        protected void Number_Handler(object sender, CommandEventArgs e)
        {
           
            switch (e.CommandName)
            {

               case "NAT":
                    LoadNumbers(0, 1);
                   break;

                case "EVE":
                   LoadNumbers(0, 2);
                    break;

                case "ODD":
                    LoadNumbers(1, 2);
                    break;
            }

        }

        private void LoadNumbers(int stratNumber, int stepNumber)
        {
            ListBox1.Items.Clear();

            for (int i = stratNumber; i <= 100; i = i + stepNumber)
            {
                ListBox1.Items.Add(i.ToString());
            }
        }

================================================
EVENTS
======

 what is an event?
 An action recognized by an object.
 
 Event_handler contains the logic to handle the action. 


    protected void Button1_Click(object sender, EventArgs e)
        {
            Employee objEmp = new Employee();
            objEmp.SalaryEvent += new Employee.SalaryDelegate(myhandler);

            objEmp.EmpName = "raju";
            objEmp.Salary = 145000;
            Response.Write(objEmp.Salary);
        }

        void myhandler(string EmpName, int Salary)
        {
            Response.Write(EmpName + " Salary " + Salary.ToString() + " is invalid");        
        }


==========
 public class Employee
    {
        public delegate void SalaryDelegate(string EmpName, int Salary);
        
        private int _salary;
        public string EmpName;
        public event SalaryDelegate SalaryEvent;

        public int Salary
        {
            get
            {
                return _salary;
            }

            set
            {
                if (value <= 50000)
                {
                    _salary = value;
                }
                else
                {
                    SalaryEvent(EmpName, value);
                }
            }
        }
    }

=================

namespace WebApplication17
{
    public class Employee
    {
        //public delegate void SalaryDelegate(string EmpName, int Salary);
        
        private int _salary;
        public string EmpName;
        public event EventHandler SalaryEvent;

        public int Salary
        {
            get
            {
                return _salary;
            }

            set
            {
                if (value <= 50000)
                {
                    _salary = value;
                }
                else
                {
                    SalaryEvent(this, new EventArgs());
                    //SalaryEvent(null, null);
                }
            }
        }
    }
}

===================

      protected void Button1_Click(object sender, EventArgs e)
        {
            Employee objEmp = new Employee();
            objEmp.SalaryEvent += new EventHandler(objEmp_SalaryEvent);

            objEmp.EmpName = "raju";
            objEmp.Salary = 145000;
            Response.Write(objEmp.Salary);
        }

        void objEmp_SalaryEvent(object sender, EventArgs e)
        {
                Employee tmpEmp = sender as Employee;

                Response.Write(tmpEmp.EmpName + " salary is invalid" ); 
        
        }
===================

    public class Employee
    {
        //public delegate void SalaryDelegate(string EmpName, int Salary);
        
        private int _salary;
        public string EmpName;
        public event EventHandler SalaryEvent;

        public int Salary
        {
            get
            {
                return _salary;
            }

            set
            {
                if (value <= 50000)
                {
                    _salary = value;
                }
                else
                {
                    SalaryEvent(null, new EmpEventData(this.EmpName, value));
                }
            }
        }
    }
    public class EmpEventData : EventArgs
    {
        public string Name;
        public int salary;

        public EmpEventData(string pName, int psalary)
        {
            this.Name = pName;
            this.salary = psalary;
        }
    }
===================


  protected void Button1_Click(object sender, EventArgs e)
        {
            Employee objEmp = new Employee();
            objEmp.SalaryEvent += new EventHandler(objEmp_SalaryEvent);

            objEmp.EmpName = "raju";
            objEmp.Salary = 145000;
            Response.Write(objEmp.Salary);
        }

        void objEmp_SalaryEvent(object sender, EmpEventData e)
        {
            Response.Write(e.Name + " salar " + e.salary.ToString() + " is invalid");
        }

    }

===================






EXTENSION METHODS
=================

1) If no source code available
2) the class is sealed class 
but still you want to extend the functionalty of the clas then you can go for extentsion methods


namespace StringExtender
{
    public static class StringExtender
    {
        public static string ToProper(this string strValue)
        {
            StringBuilder sb = new StringBuilder();

            string[] myWords = strValue.Split(' ');

            foreach (string st in myWords)
            {
                sb.Append(st.Substring(0, 1).ToUpper());
                sb.Append(st.Substring(1).ToLower());
                sb.Append(" ");
            }
            return sb.ToString();
        }
    }
}

using StringExtender;


namespace WebApplication17
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            string st = "ravi kuMar KVS, gss Info TEch, Hyderabad";
            Response.Write(st.ToProper());
       }

    }
}