using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Web.UI.HtmlControls;
using System.Configuration;
using System.Collections;

namespace WebApplication21
{
    public partial class WebForm2 : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            SqlConnection MyConn;
            SqlCommand MyCmd;
            SqlDataReader MyRdr;
            String MyString = "Data Source= .\\SQLEXPRESS; AttachDbFilename=|DataDirectory|\\Databasebest.mdf; Integrated Security=true; User Instance=true";
            MyConn = new SqlConnection(MyString);
           
            if (!IsPostBack)
            {
                MyConn.Open();

                MyCmd = new SqlCommand("SELECT * FROM Catalogue", MyConn);
                MyRdr = MyCmd.ExecuteReader();
                DropDownList1.DataSource = MyRdr;
                DropDownList1.DataValueField = "Price";
                DropDownList1.DataTextField = "Code";
                DropDownList1.DataBind();
                MyRdr.Close();
            }  
        }
        protected void rebind()
        {

        }

        protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            SqlConnection MyConn;
            SqlCommand MyCmd;
            SqlDataReader MyRdr;
            String MyString = "Data Source= .\\SQLEXPRESS; AttachDbFilename=|DataDirectory|\\Databasebest.mdf; Integrated Security=true; User Instance=true";
            MyConn = new SqlConnection(MyString);
            MyCmd = new SqlCommand("SELECT * FROM Catalogue WHERE [Code] LIKE @Code", MyConn);
            MyCmd.Parameters.AddWithValue("@Code", DropDownList1.SelectedItem.Value);
            MyConn.Open();
            MyRdr = MyCmd.ExecuteReader();
            while (MyRdr.Read())
            {
                product_NamTB.Text = (string)MyRdr["Product_Name"];
                pricTB.Text = (string)MyRdr["Price"];
            }
            MyRdr.Close();
            MyConn.Close();
        }

        protected void Button1_Click(object sender, EventArgs e)
        {
        SqlConnection MyConn;
        SqlCommand MyCmd;
        String MyString = "Data Source= .\\SQLEXPRESS; AttachDbFilename=|DataDirectory|\\Databasebest.mdf; Integrated Security=true; User Instance=true";
        MyConn = new SqlConnection(MyString);
        MyCmd = new SqlCommand("INSERT INTO Catalogue (Product_Name, Code, Price) VALUES (@Product_Name, @Code, @Price)", MyConn);
// update the command with the parameters from the text box’s
        MyCmd.Parameters.AddWithValue("@product_Name", product_NameTB.Text);
        MyCmd.Parameters.AddWithValue("@Code", CodeTB.Text);
        MyCmd.Parameters.AddWithValue("@Price", PriceTB.Text);
        MyConn.Open(); // open the connection
// run the query, this method is used as it does not return a value
        MyCmd.ExecuteNonQuery(); 
        MyConn.Close(); // close the connection
       }

       protected void Button2_Click(object sender, EventArgs e)
       {
       SqlConnection MyConn;
       SqlCommand MyCmd;
       String MyString = "Data Source= .\\SQLEXPRESS; AttachDbFilename=|DataDirectory|\\Databasebest.mdf; Integrated Security=true; User Instance=true";
       MyConn = new SqlConnection(MyString);
       MyCmd = new SqlCommand("UPDATE Catalogue SET [Product_Name] =@Product_Name, [Price] =@Price WHERE Code LIKE @Code", MyConn);
       MyCmd.Parameters.AddWithValue("@code", DropDownList1.SelectedItem.Value);
       MyCmd.Parameters.AddWithValue("@Product_Name", product_NamTB.Text);
       MyCmd.Parameters.AddWithValue("@Price", pricTB.Text);
       MyConn.Open();
       MyCmd.ExecuteNonQuery();
       MyConn.Close();
       Response.Redirect("WebForm2.aspx");
       }

       protected void Button3_Click(object sender, EventArgs e)
       {
           SqlConnection MyConn;
           SqlCommand MyCmd;
           String MyString = "Data Source= .\\SQLEXPRESS; AttachDbFilename=|DataDirectory|\\Databasebest.mdf; Integrated Security=true; User Instance=true";
           MyConn = new SqlConnection(MyString);
           MyCmd = new SqlCommand("DELETE FROM Catalogue WHERE [Code] LIKE @Code ", MyConn);
           MyCmd.Parameters.AddWithValue("@code", DropDownList1.SelectedItem.Value);
           MyConn.Open(); 
// run the query, this method is used as it does not return a value
           MyCmd.ExecuteNonQuery();
           MyConn.Close(); 
       }
    }

}

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm2.aspx.cs" Inherits="WebApplication21.WebForm2" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
    <form id="form1" runat="server">
     <div>
     Product_Name<br />
     <asp:TextBox ID="product_NameTB" runat="server" >
     </asp:TextBox>
     <br />Code<br />
	 <asp:TextBox ID="CodeTB" runat="server" >
     </asp:TextBox>
     <br />Price<br />
     <asp:TextBox ID="PriceTB" runat="server" >
     </asp:TextBox>
     <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Add" />
     <br />
     <br />
     <br />
     <asp:DropDownList ID="DropDownList1" runat="server" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
     </asp:DropDownList>
     <br />Product_Name<br />
     <asp:TextBox ID="product_NamTB" runat="server"></asp:TextBox>
     <br />Price<br />
     <asp:TextBox ID="pricTB" runat="server"></asp:TextBox>
     <asp:Button ID="Button2" runat="server" OnClick="Button2_Click" Text="Update" />
     <br />
     <br />
     <br />
     <asp:Button ID="Button3" runat="server" OnClick="Button3_Click" Text="Delete" />
     
     </div>
     </form>
</body>
</html>