In this article I will explain how to use jQuery Autocomplete plugin with ASP.Net Web Services, I have already wrote article on jQuery Autocomplete using ASP.Net Generic Handler
For database I am using the Microsoft’s NorthWind Database. You can download the same using the link below
Connection String
Below is the connection string to the database which I have placed in the web.config.
    <addname="constr"connectionString="Data Source = .\SQL2005;       
       Initial Catalog = Northwind; Integrated Security = true"/>
Building the Web Service
Below is the code for the web service which will handle the jQuery Autocomplete calls and will return the matching records from the Customers table of the Northwind database.
The select query gets the Name and the ID of the customer that matches the prefix text.
The fetched records are processed and the Key Value Pair is created by appending the Id to the Name field in the following format {0}-{1} where is the Name {0} and {1} is the ID.
using System;
using System.Collections.Generic;
using System.Web;
using System.Web.Services;
using System.Data.SqlClient;
using System.Configuration;
using System.Web.Script.Services;
/// Summary description for Service
[WebService(Namespace = "")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
// To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line.
public class Service : System.Web.Services.WebService {
    public Service () {
        //Uncomment the following line if using designed components
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public string[] GetCustomers(string prefix)
        List<string> customers = new List<string>();
        using (SqlConnection conn = new SqlConnection())
            conn.ConnectionString = ConfigurationManager
            using (SqlCommand cmd = new SqlCommand())
                cmd.CommandText = "select ContactName, CustomerId from Customers where " +
                "ContactName like @SearchText + '%'";
                cmd.Parameters.AddWithValue("@SearchText", prefix);
                cmd.Connection = conn;
                using (SqlDataReader sdr = cmd.ExecuteReader())
                    while (sdr.Read())
                        customers.Add(string.Format("{0}-{1}", sdr["ContactName"], sdr["CustomerId"]));
            return customers.ToArray();
Imports System.Web
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.Web.Script.Services
Imports System.Data.SqlClient
Imports System.Collections.Generic
' To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line.
' <System.Web.Script.Services.ScriptService()> _
<WebService(Namespace:="")> _
<WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _
<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
<ScriptService()> _
Public Class Service
    Inherits System.Web.Services.WebService
    <WebMethod()> _
    <ScriptMethod(ResponseFormat:=ResponseFormat.Json)> _
    Public Function GetCustomers(ByVal prefix As String) As String()
        Dim customers As New List(Of String)()
        Using conn As New SqlConnection()
            conn.ConnectionString = ConfigurationManager.ConnectionStrings("constr").ConnectionString
            Using cmd As New SqlCommand()
                cmd.CommandText = "select ContactName, CustomerId from Customers where " & "ContactName like @SearchText + '%'"
                cmd.Parameters.AddWithValue("@SearchText", prefix)
                cmd.Connection = conn
                Using sdr As SqlDataReader = cmd.ExecuteReader()
                    While sdr.Read()
                        customers.Add(String.Format("{0}-{1}", sdr("ContactName"), sdr("CustomerId")))
                    End While
                End Using
            End Using
            Return customers.ToArray()
        End Using
    End Function
End Class
Client Side Implementation
Populating the Autocomplete list
In the client side implementation the data received from the server is processed in the success event handler. A loop is executed for each received item in the list of items and then an object with text part in the label property and value part in the val property is returned.
Storing the Value part when item is selected
In the select event handler of the jQuery Autocomplete I am storing the value (Here Customer ID) in the hfCustomerId Hidden Field so that it can be fetched server side.
<html xmlns="">
<head id="Head1" runat="server">
<script src=""
type = "text/javascript"></script>
<script src=""
type = "text/javascript"></script>
<link href=""
rel = "Stylesheet" type="text/css" />
<script type="text/javascript">
    $(document).ready(function () {
        $("#<%=txtSearch.ClientID %>").autocomplete({
            source: function (request, response) {
                    url: '<%=ResolveUrl("~/Service.asmx/GetCustomers") %>',
                    data: "{ 'prefix': '" + request.term + "'}",
                    dataType: "json",
                    type: "POST",
                    contentType: "application/json; charset=utf-8",
                    success: function (data) {
                        response($.map(data.d, function (item) {
                            return {
                                label: item.split('-')[0],
                                val: item.split('-')[1]
                    error: function (response) {
                    failure: function (response) {
            select: function (e, i) {
                $("#<%=hfCustomerId.ClientID %>").val(i.item.val);
            minLength: 1
    <form id="form1" runat="server">
    <asp:TextBox ID="txtSearch" runat="server"></asp:TextBox>
    <asp:HiddenField ID="hfCustomerId" runat="server" />
    <br />
    <asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick = "Submit" />
Fetching the Selected Item Key and Value server side
The Key (Here Customer Name) and Value (Here Customer ID) can be fetched server side on click of submit button in the following way
protected void Submit(object sender, EventArgs e)
    string customerName = Request.Form[txtSearch.UniqueID];
    string customerId = Request.Form[hfCustomerId.UniqueID];
Protected Sub Submit(ByVal sender As Object, ByVal e As System.EventArgs)
   Dim customerName As String = Request.Form(txtSearch.UniqueID)
  Dim customerId As String = Request.Form(hfCustomerId.UniqueID)
End Sub
Working of the jQuery Autocomplete using Web Services
Implementing jQuery Autocomplete Plugin with ASP.Net Web services
Fetching the Key and Value of the selected Autocomplete Item
Fetching the jQuery Autocomplete Key Value Pair Server side
Browser Compatibility
The above code has been tested in the following browsers.

Internet Explorer  FireFox  Chrome  Safari  Opera 


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Download Code