Ajax AutoComplete in ASP.NET

A Technical Blog article. View original blog here.[^]

Without using AjaxControlToolKit, we can implement AutoComplete Extender using pure Ajax Call. This article explains how to do make AutoComplete Extender.

OnKeyUp event helps you to fetch data from database with Ajax call. Here one Handler.ashx handles the AJAX request form Client. I add a Class file to handle database operations to better coding practice. Below I explain the database helper Class. Class has one method:

GetTable(string sqlQuery)

This returns DataTable after fetching data from database. And also includes Provide Class, this Class helps to get SqlConnection string.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Data.SqlClient;
using System.Configuration;
using System.Data;
/// <summary>
/// Summary description for DBHelper
/// </summary>
public class DBHelper
{
    SqlConnection connection;
    SqlDataAdapter adapter;
    SqlCommand command;
    DataTable dataTable;
    public DBHelper()
    {
    }
    /// <summary>
    /// 
    /// </summary>
    /// <param name="sqlQuery">passing SQL Query here
    /// <returns>DataTable object is returned</returns>
    public DataTable GetTable(string sqlQuery)
    {
        //creating new instance of Datatable
        dataTable = new DataTable();
        connection = Provider.GetConnection();
        command = new SqlCommand(sqlQuery, connection);
        //Open SQL Connection
        connection.Open();
            try
            {
                adapter = new SqlDataAdapter(command);
                adapter.Fill(dataTable);
            }
            catch
            { }
            finally
            {
                //Closing Sql Connection 
                connection.Close();
            }
        return dataTable;
    }
}
public class Provider
{
    public static SqlConnection GetConnection()
    {
        //creating SqlConnection
        return new SqlConnection(ConfigurationManager.AppSettings["sqlConn"]);
    }
}

Now we can look into Handler file. When request comes from Ajax Call from Client, it passes the data into our Database helper Class, handler file holds the data in DataTable. Result data are formatted in a table and written in the context. We can add JavaScript function for selecting the data, here api_helper.AddtoTaxtBox(selectedItem) manages client section of data.

Check Handler File

<%@ WebHandler Language="C#" Class="Handler" %>
using System;
using System.Web;
using System.Data;
public class Handler : IHttpHandler {
    public void ProcessRequest (HttpContext context) {

        HttpRequest request = HttpContext.Current.Request;
        //checking string null or empty
        if (!string.IsNullOrEmpty(request.QueryString["name"]))
        {
            string name=request.QueryString["name"];
            //creating instance of new database helper
            DBHelper objDBHelper = new DBHelper();
            //creating Sql Query
            string sqlQuery = string.Format
		("SELECT Name FROM User WHERE Name LIKE '{0}%'", name);
            //filling data from database
            DataTable dataTable = objDBHelper.GetTable(sqlQuery);

             string table = string.Empty;
            //table for hold data
            table = "<table width='100%'>";
            string td = string.Empty;
            //checking datatable
                if (dataTable.Rows.Count > 0)
                {
                    for (int i = 0; i < dataTable.Rows.Count; i++)
                    {
                        //adding table rows
                        td += string.Format("<tr><td class='select' 
			onclick='api_helper.AddtoTaxtBox(this.innerHTML)'>
			{0}</td></tr>", dataTable.Rows[i][0].ToString());
                    }
                }
                table += td + "</table>";
                context.Response.Write(table);
        }
    }
    public bool IsReusable {
        get {
            return false;
        }
    }
}

Now we can check how Ajax works. On Textbox onKeyUp event, call the Ajax code. It sends the entered value into server using Ajax and the result is displayed in div control under the search textbox.

<%@ 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></title>
</head>
<body>
     <form id="form1" runat="server">
       <div>

         <asp:TextBox ID="txtName" runat="server" 
		onkeyup="api_helper.callAjax();"></asp:TextBox>
           <div id="myDiv"></div>
           
      </div>
             <script language="javascript" type="text/javascript">

               if (typeof (api_helper) == 'undefined') { api_helper = {} }

               api_helper.doAjax = function(HandlerUrl, displayDiv) {
                var Req; try { Req = new XMLHttpRequest(); } 
		catch (e) { try { Req = new ActiveXObject("Msxml2.XMLHTTP"); }
		catch (e) { try { xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); } 
		catch (e) { return false; } } } Req.onreadystatechange = function() {
		if (Req.readyState == 4) { var d = document.getElementById(displayDiv); 
		d.innerHTML = Req.responseText; } }
                Req.open("GET", HandlerUrl, true); Req.send(null);
              }

               api_helper.callAjax = function() {
                var text = document.getElementById("txtName").value;
                if (text != "") {
                    var requestUrl = "Handler.ashx?name=" + text;
                    var displayDiv="myDiv";
                    api_helper.doAjax(requestUrl, displayDiv);
                }
              }

              api_helper.AddtoTaxtBox = function(txt) {
                document.getElementById("txtName").value = txt;
                document.getElementById("myDiv").innerHTML = "";
              }
            </script>         
     </form>
  </body>
</html>