AJAX AutoComplete:

AutoComplete is an ASP.NET AJAX extender that can be attached to any TextBox control, and will associate that control with a popup panel to display list of words that begin with the prefix typed into the textbox.

If you want to implement custom CSS style to AutoComplete Extender please refer this article. 

Custom CSS style for AJAX AutoComplete Extender

Here I’m going to demonstrate you, the textbox is associated with an AutoCompleteExtender that pulls words that start with the contents of the textbox using a web service.

AJAX AutoComplete properties:

<asp:AutoCompleteExtender ID="AutoCompleteExtender1"










       TargetControlID - The TextBox control where the user types content to be automatically completed

   MinimumPrefixLength - Minimum number of characters that must be entered before getting suggestions from the web service.

             EnableCaching - Whether client side caching is enabled.

           CompletionSetCount - Number of suggestions to be retrieved from the web service.

   ServiceMethod - The web service method to be called. The signature of this method must match the following:

Sample code: 




       public static List<string> GetCity(string prefixText)





You can refer AutoComplete complete properties here



First we have to create a table. Sample table design given below


 Table design (City):

Column Name

Data Type






In we.config  file we have to set connection string

Sample code: 


        <add name="ConnectionString" connectionString="Data Source=localhost;                           

                                        Initial Catalog=Demo; Integrated Security=True"/>



Here we have to add AjaxControlToolkit assembly reference in our page 

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %>

 Then we have to create our aspx page like this


Designer source code:


<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %>

<!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>AJAX AutoComplete</title>



    <form id="form1" runat="server">  

    <asp:ScriptManager ID="ScriptManager1" runat="server">



    <asp:TextBox ID="txtCity" runat="server"></asp:TextBox>

    <asp:AutoCompleteExtender ID="AutoCompleteExtender1" runat="server" TargetControlID="txtCity"

         MinimumPrefixLength="1" EnableCaching="true" CompletionSetCount="1" CompletionInterval="1000"

         ServiceMethod="GetCity" >







C# code: 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Data;

using System.Data.SqlClient;

using System.Configuration; 

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


    protected void Page_Load(object sender, EventArgs e)

    {   }  



    public static List<string> GetCity(string prefixText)


        DataTable dt = new DataTable();

        string constr = ConfigurationManager.ConnectionStrings["ConnectionString"].ToString();

        SqlConnection con = new SqlConnection(constr);


        SqlCommand cmd = new SqlCommand("select * from City where CityName like @City+'%'", con);

        cmd.Parameters.AddWithValue("@City", prefixText);

        SqlDataAdapter adp = new SqlDataAdapter(cmd);       


        List<string> CityNames = new List<string>();

        for (int i = 0; i < dt.Rows.Count; i++)




        return CityNames;



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