Ajax

Here is the solution

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" tagprefix="ajaxToolkit"%>

Which says that the reference assembly "AjaxControlToolkit.dll" should be registered on the page by using above method. We should also have tagprefix="ajaxToolkit" which is similar to <ajaxToolkit: AutoCompleteExtender>.

In this article I have very simple database table called as "Tbl_Countries" with fields as:

CountryId int   primary key,
CountryName varchar(50)

I am using a web service called as "AutoComplete.asmx" whose code behind gets automatically added to the "App_Code" folder.

Note: Very important part is you need to give a reference of "AjaxControlToolkit.dll".

Here is complete code for "AutoComplete.asms.cs".

using System;

using System.Web;

using System.Collections;

using System.Web.Services;

using System.Web.Services.Protocols;

using System.Data;

using System.Data.SqlClient;

using System.Configuration;

/// <summary>

/// Summary description for AutoComplete

/// </summary>

[WebService(Namespace = "https://tempuri.org/")]

[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]

[System.Web.Script.Services.ScriptService]

public class AutoComplete : System.Web.Services.WebService

{

    [WebMethod]

    public string[] GetCountriesList(string prefixText)

    {

        DataSet dtst = new DataSet();

        SqlConnection sqlCon = new SqlConnection(ConfigurationManager.AppSettings["ConnectionString"]);

        string strSql = "SELECT CountryName FROM Tbl_Countries WHERE CountryName LIKE '" + prefixText + "%' ";

        SqlCommand sqlComd = new SqlCommand(strSql, sqlCon);

        sqlCon.Open();

        SqlDataAdapter sqlAdpt = new SqlDataAdapter();

        sqlAdpt.SelectCommand = sqlComd;

        sqlAdpt.Fill(dtst);

        string[] cntName = new string[dtst.Tables[0].Rows.Count];

        int i = 0;

        try

        {

            foreach (DataRow rdr in dtst.Tables[0].Rows)

            {

                cntName.SetValue(rdr["CountryName"].ToString(), i);

                i++;

            }

        }

        catch { }

        finally

        {

            sqlCon.Close();

        }

        return cntName;

    }

}

Let us take another page called as "default.aspx" in which I am having a <scriptmanager> tag and in which a <service> tag in which you can specify path of webservices. You have already registered Assembly="AjaxControlToolkit" on this page so you can use that.

So my entire code will look something like this

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

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" tagprefix="ajaxToolkit"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "https://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">

<html xmlns="https://www.w3.org/1999/xhtml">

<head id="Head1" runat="server">

    <title>Untitled Page</title>

</head>

<body>

    <form id="form1" runat="server">

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

            <Services>

                <asp:ServiceReference Path="AutoComplete.asmx" />

            </Services>

        </asp:ScriptManager>

        <div>

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

            <ajaxToolkit:AutoCompleteExtender runat="server" ID="autoComplete1" TargetControlID="txtCountry" ServicePath="AutoComplete.asmx" ServiceMethod="GetCountriesList" MinimumPrefixLength="1" EnableCaching="true" />

        </div>

    </form>

</body>

</html>