How to Use Delegate in ASP.NET using C#

Delegate is like variable it is not a method. it invoke method Suppose if you want to call numbers of method with same parameter so you can use delegate which is more fast and it reduce you code see following example

using System;

using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq; 

public partial class delegatewith2arg : System.Web.UI.Page
{ 

    public delegate void calculation(double a, double b);  //  define delegate
    protected void Page_Load(object sender, EventArgs e)
    {
 
    }
    protected void btnok_Click(object sender, EventArgs e)
    {
        calculation calc = sum;        // invoke first method
        calc += minus;                   //invoke second
        calc += multiply;                // third
        calc += devide;                 // forth
        calc.Invoke(double.Parse(txtfirstvalue.Text), double.Parse(txtsecondvalue.Text));   // pass value as arguemet
    } 

    void sum(double x, double y)                 // first method
    {
        lblsum.Text = (x + y).ToString();
    }
    void minus(double x, double y)            // second method
    {
        lblminus.Text = (x - y).ToString();
    }
    void multiply(double x, double y)        // third method
    {
        lblmultiply.Text = (x * y).ToString();
    }
    void devide(double x, double y)        //forth method
    {
        lbldevide.Text = (x / y).ToString();
    }
}