Sample Image - maximum width is 600 pixels

Introduction

This is very simple code which makes an Auto Complete Combo with database.

It's useful. First of all, you do not have to know about Ajax functions, just download the AJAX Control Toolkit on CodePlex and follow me, then enjoy. Besides when there are many rows, you can type part of the word in the text box, then it can offer all of the words which are similar to it.

Background: What is Ajaxcontroltoolkit?

The ASP.NET AJAX Control Toolkit is an open-source project built on top of the Microsoft ASP.NET AJAX framework and contains more than 30 controls that enable you to easily create rich, Interactive web pages. If you want to know more about it, visit this link.

Using the Code

It the first step, you must download AjaxControlToolkit from here for .NET 3.5 OR here for .NET 4.0.

You must go here and download ajaxcontroltoolkit, then Copy ajaxcontroltoolkit and paste them to Bin Folder, right click on solution, choose Add Reference, in the browse tab double click on the Bin Folder, and double click on ajaxcontroltoolkit, then on the Build Menu > click Rebuild.

DataBase

New Query

CREATE TABLE [dbo].[tblCustomer](
	    [CompanyName] [nvarchar](500) NULL,
	    [ID] [int] IDENTITY(1,1) NOT NULL
        ) ON [PRIMARY]

insert into dbo.tblCustomer(CompanyName) values('calemard')
insert into dbo.tblCustomer(CompanyName) values('dantherm')
insert into dbo.tblCustomer(CompanyName) values('dango dienenthal')
insert into dbo.tblCustomer(CompanyName) values('daewoo')
insert into dbo.tblCustomer(CompanyName) values('daim engineering')

Visual Studio 2008 - .NET 3.5: Create Web Site and name it AutoComplete, create Web Form and name it AutoComplete.aspx, in HTML view, write this code.
But there is a little difference between C# and VB in this section.

This code in the bottom is for C# coders.
If you are a VB coder, please modify 2 sections in page tag
1. One: correct language=VB
2. Two: correct CodeFile="AutoComplete.aspx.vb"

<%@ Page Language="C#" AutoEventWireup="false"
         CodeFile="AutoComplete.aspx.cs" Inherits="AutoComplete" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit"
         TagPrefix="ajaxToolkit" %>
<!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>AutoComplete</title>
<link href="StyleSheet.css" rel="stylesheet" type="text/css" />
</head>
<body>
<form id="form1" runat="server">
<ajaxToolkit:ToolkitScriptManager  ID="ScriptManager1" runat="server">
</ajaxToolkit:ToolkitScriptManager>
<ajaxToolkit:AutoCompleteExtender ID="autoComplete1" runat="server"
  EnableCaching="true"
  BehaviorID="AutoCompleteEx"
  MinimumPrefixLength="2"
  TargetControlID="myTextBox"
  ServicePath="AutoComplete.asmx"
  ServiceMethod="GetCompletionList" 
  CompletionInterval="1000"  
  CompletionSetCount="20"
  CompletionListCssClass="autocomplete_completionListElement"
  CompletionListItemCssClass="autocomplete_listItem"
  CompletionListHighlightedItemCssClass="autocomplete_highlightedListItem"
  DelimiterCharacters=";, :"
  ShowOnlyCurrentWordInCompletionListItem="true">
  <Animations>
  <OnShow>
  <Sequence>
  <%-- Make the completion list transparent and then show it --%>
  <OpacityAction Opacity="0" />
  <HideAction Visible="true" />

  <%--Cache the original size of the completion list the first time
    the animation is played and then set it to zero --%>
  <ScriptAction Script="// Cache the size and setup the initial size
                                var behavior = $find('AutoCompleteEx');
                                if (!behavior._height) {
                                    var target = behavior.get_completionList();
                                    behavior._height = target.offsetHeight - 2;
                                    target.style.height = '0px';
                                }" />
  <%-- Expand from 0px to the appropriate size while fading in --%>
  <Parallel Duration=".4">
  <FadeIn />
  <Length PropertyKey="height" StartValue="0" 
	EndValueScript="$find('AutoCompleteEx')._height" />
  </Parallel>
  </Sequence>
  </OnShow>
  <OnHide>
  <%-- Collapse down to 0px and fade out --%>
  <Parallel Duration=".4">
  <FadeOut />
  <Length PropertyKey="height" StartValueScript=
	"$find('AutoCompleteEx')._height" EndValue="0" />
  </Parallel>
  </OnHide>
  </Animations>
  </ajaxToolkit:AutoCompleteExtender>
<asp:TextBox ID="myTextBox" autocomplete ="off" runat="server"></asp:TextBox>

</form>
</body>
</html>

For StyleSheet (CSS file)

Create StyleSheet: Solution > Right Click > Add New Item > Web Service >
Name: StyleSheet.css
Language: Visual Basic OR C#
Go To > StyleSheet.css (File) > Ctrl+A (Select All) > Delete
Go to this section (below) > Select this code > Ctrl+C >
Go To StyleSheet.css (file) > Ctrl+V (paste)

/*AutoComplete flyout */
.autocomplete_completionListElement
{
    margin : 0px!important ;
    background-color : inherit ;
    color : windowtext ;
    border : buttonshadow ;
    border-width : 1px ;
    border-style : solid ;
    cursor : 'default' ;
    overflow : auto ;
    height : 200px ;
    font-family : Tahoma ;
    font-size : small ;
    text-align : left ;
    list-style-type : none ;
    }
/* AutoComplete highlighted item */
.autocomplete_highlightedListItem
   {
    background-color : #ffff99 ;
    color : black ;
    padding : 1px ;
    }

    /* AutoComplete item */
.autocomplete_listItem
    {
    background-color : window ;
    color : windowtext ;
    padding : 1px ;
   }

For VB

Create Web Service: Solution > Right Click > Add New Item > Web Service >
Name: AutoComplete.asmx
Language: Visual Basic
Go To > App_Code > AutoComplete.vb

' (c) Copyright Microsoft Corporation.
' This source is subject to the Microsoft Public License.
' See http://www.microsoft.com/opensource/licenses.mspx#Ms-PL.
' All other rights reserved.
Imports System
Imports System.Collections
Imports System.Linq
Imports System.Web
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.Xml.Linq
Imports System.Collections.Generic
Imports System.Data
Imports System.Data.SqlClient

' 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:="http://tempuri.org/")> _
<WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _
Public Class AutoComplete
    Inherits System.Web.Services.WebService
    Dim cn As New SqlClient.SqlConnection()
    Dim ds As New DataSet
    Dim dt As New DataTable
<WebMethod()> _
Public Function GetCompletionList(ByVal prefixText As String, _
	ByVal count As Integer) As String()

        'ADO.Net
        Dim strCn As String = _
		"data source=.;Initial Catalog=MyDB;Integrated Security=True"
        cn.ConnectionString = strCn
        Dim cmd As New SqlClient.SqlCommand
        cmd.Connection = cn
        cmd.CommandType = CommandType.Text
        'Compare String From Textbox(prefixText) 
        'AND String From Column in DataBase(CompanyName)
        'If String from DataBase is equal to String from TextBox(prefixText) 
        'then add it to return ItemList
        '-----I defined a parameter instead of passing value 
        'directly to prevent SQL injection--------'
        cmd.CommandText = "select * from tblCustomer Where CompanyName like @myParameter"
        cmd.Parameters.AddWithValue("@myParameter", "%" + prefixText + "%")

        Try
            cn.Open()
            cmd.ExecuteNonQuery()
            Dim da As New SqlDataAdapter(cmd)
            da.Fill(ds)
        Catch ex As Exception
        Finally
            cn.Close()
        End Try

        dt = ds.Tables(0)

        'Then return List of string(txtItems) as result

        Dim txtItems As New List(Of String)
        Dim dbValues As String

        For Each row As DataRow In dt.Rows

            ''String From DataBase(dbValues)
            dbValues = row("CompanyName").ToString()
            dbValues = dbValues.ToLower()
            txtItems.Add(dbValues)

        Next

        Return txtItems.ToArray()

    End Function

End Class

For C#

Web Service: Solution > Right Click > Add New Item > Web Service >
Name: AutoComplete.asmx
Language: C#
Go To > App_Code > AutoComplete.cs

// (c) Copyright Microsoft Corporation.
// This source is subject to the Microsoft Public License.
// See http://www.microsoft.com/opensource/licenses.mspx#Ms-PL.
// All other rights reserved.
using System;
using System.Collections;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Web.Services.Protocols;
using System.Xml.Linq;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;

///<summary>
/// Summary description for AutoComplete
///</summary>

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
// To allow this Web Service to be called from script, using ASP.NET AJAX, 
// uncomment the following line.
[System.Web.Script.Services.ScriptService]
public class AutoComplete : System.Web.Services.WebService {

    public AutoComplete () {

        //Uncomment the following line if using designed components
        //InitializeComponent();
    }

    [WebMethod]
    public string[] GetCompletionList(string prefixText, int count)
    {
        //ADO.Net
        SqlConnection cn =new SqlConnection();
        DataSet ds = new DataSet();
        DataTable  dt = new DataTable();
        String strCn = "data source=.;Initial Catalog=MyDB;Integrated Security=True";
        cn.ConnectionString = strCn;
        SqlCommand cmd = new SqlCommand();
        cmd.Connection = cn;
        cmd.CommandType = CommandType.Text;
        //Compare String From Textbox(prefixText) AND String From 
        //Column in DataBase(CompanyName)
        //If String from DataBase is equal to String from TextBox(prefixText) 
        //then add it to return ItemList
        //-----I defined a parameter instead of passing value directly to 
        //prevent SQL injection--------//
        cmd.CommandText = "select * from tblCustomer Where CompanyName like @myParameter";
        cmd.Parameters.AddWithValue("@myParameter", "%" + prefixText + "%");

        try
        {
            cn.Open();
            cmd.ExecuteNonQuery();
            SqlDataAdapter da = new SqlDataAdapter(cmd);
            da.Fill(ds);
        }
        catch
        {
        }
        finally
        {
            cn.Close();
        }
        dt = ds.Tables[0];

	    //Then return List of string(txtItems) as result
        List<string> txtItems =new List<string>();
        String  dbValues;

        foreach (DataRow row  in dt.Rows)
        {
             //String From DataBase(dbValues)
            dbValues = row["CompanyName"].ToString();
            dbValues = dbValues.ToLower();
            txtItems.Add(dbValues);
        }

        return txtItems.ToArray();
    }
}

Summary

GetCompletionList is a function that catches 2 arguments, prefixText as string and count as int.

When you type some characters, they are saved in prefixText and number of your characters are saved in count. And at the end, function returns list of string (they are similar to your characters) which has been obtained as follows:

I have written some code in ADO.NET section, these rows have been filtered by prefixText, which are similar to your characters that are typed in text box.
Additionally, I defined a parameter instead of passing value directly to prevent SQL injection.

I create txtItems in List of string data type, we can save words that we want. Then in a foreach loop, I converted them into tolower, I added those values to my result value (txtItems), finally I return txtItems.

Try Step by Step

Feedback

Feel free to leave any feedback on this article; it is a pleasure to see your comments and vote about this code. If you have any questions, please do not hesitate to ask me here.

AutoComplete With DataBase and AjaxControlToolkit