Hi Zuber,
Try this...
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="Ajax_dropdown._Default" %>
<!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>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:UpdatePanel ID="up1" runat="server">
<ContentTemplate >
<asp:Label ID="Label1" runat="server" Text="Choose City" BackColor="#FFFF99"
ForeColor="Red" Width="100px"></asp:Label><br />
<asp:DropDownList ID="DropDownList1" AutoPostBack ="true"
AppendDataBoundItems="true" runat="server" Height="20px" Width="156px"
onselectedindexchanged="DropDownList1_SelectedIndexChanged" Font-Bold="True"
ForeColor="#FF9900">
</asp:DropDownList><br />
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID ="DropDownList1" />
</Triggers>
</asp:UpdatePanel>
</div>
</form>
</body>
</html>
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;
using System.Data.SqlClient;
namespace Ajax_dropdown
{
public partial class _Default : System.Web.UI.Page
{
string strConnString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
string str;
SqlCommand com;
protected void Page_Load(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection(strConnString);
if (!IsPostBack)
{
DropDownList1.Items.Add("Choose City");
con.Open();
str = "select * from area ";
com = new SqlCommand(str, con);
SqlDataReader reader = com.ExecuteReader();
while (reader.Read())
{
DropDownList1.Items.Add(reader["city"].ToString());
}
reader.Close();
con.Close();
}
TextBox1.Text = "";
TextBox1.Enabled = false;
}
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
TextBox1.Enabled = true;
SqlConnection con = new SqlConnection(strConnString);
con.Open();
str = "select * from area where city='" + DropDownList1.SelectedValue + "'";
com = new SqlCommand(str, con);
SqlDataReader reader = com.ExecuteReader();
while (reader.Read())
{
TextBox1.Text = reader["stdcode"].ToString();
}
reader.Close();
con.Close();
}
}
}
Thanks
If this post helps you mark it as answer