In this blog we will know when selected any item from the dropdown list all records related to this will be displayed in a grid view without refreshing the whole webpage.

Table Creation

Create table Contacts (id varchar(50),name varchar(50),city varchar(50))

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_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 Name" BackColor="#FFFF99"

ForeColor="Red" Width="100px"></asp:Label>

<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True"

onselectedindexchanged="DropDownList1_SelectedIndexChanged" >

</asp:DropDownList>

</ContentTemplate>

<Triggers>

<asp:AsyncPostBackTrigger ControlID ="DropDownList1" />

</Triggers>

</asp:UpdatePanel>

<br />

<asp:UpdatePanel ID="up2" runat="server">

<ContentTemplate >

<asp:GridView ID="GridView1" runat="server">

</asp:GridView>

</ContentTemplate>

<Triggers >

<asp:AsyncPostBackTrigger ControlID ="GridView1" />

</Triggers>

</asp:UpdatePanel>

<br />

</div>

</form>

</body>

</html>

using System;

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;

public partial class _Default : System.Web.UI.Page

{

string connStr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;

SqlDataAdapter ad = new SqlDataAdapter();

SqlCommand cmd = new SqlCommand();

SqlDataAdapter sqlda;

DataSet ds;

string str;

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)

{

SqlConnection conn = new SqlConnection(connStr);

conn.Open();

str = "select * from Contacts where name like '" + DropDownList1.SelectedValue + "'";

cmd = new SqlCommand(str, conn);

sqlda = new SqlDataAdapter(cmd);

ds = new DataSet();

sqlda.Fill(ds, "Contacts");

conn.Close();

GridView1.DataSource = ds;

GridView1.DataMember = "Contacts";

GridView1.DataBind();

}

protected void Page_Load(object sender, EventArgs e)

{

SqlConnection con = new SqlConnection(connStr);

if (!IsPostBack)

{

DropDownList1.Items.Add("Choose name");

con.Open();

str = "select name from Contacts";

cmd = new SqlCommand(str, con);

SqlDataReader reader = cmd.ExecuteReader();

while (reader.Read())

{

DropDownList1.Items.Add(reader["name"].ToString());

}

reader.Close();

con.Close();

}

}

}