How to Implement Autocomplete textbox in ASP.NET WITHOUT using Webservice & AJAX autocomplete extender

Step - 1: Create New Project.

Go to File > New > Project > Select asp.net web forms application > Entry Application Name > Click OK.

Step-2: Add a Database.

Go to Solution Explorer > Right Click on App_Data folder > Add > New item > Select SQL Server Database Under Data > Enter Database name > Add.

Step-3: Create table for fetch data.

Open Database > Right Click on Table > Add New Table > Add Columns > Save > Enter table name > Ok.

In this example, I have used one table as below

Step-4: Add Entity Data Model.

Go to Solution Explorer > Right Click on Project name form Solution Explorer > Add > New item > Select ADO.net Entity Data Model under data > Enter model name > Add.
A popup window will come (Entity Data Model Wizard) > Select Generate from database > Next >

Chose your data connection > select your database > next > Select tables > enter Model Namespace > Finish.

Step-5: Add a Webpage and Design for implementing Autocomplete textbox.

Go to Solution Explorer > Right Click on Project name form Solution Explorer > Add > New item > Select web form/ web form using master page under Web > Enter page name > Add.

HTML Code 

<h3>Auto Complete Textbox without using Web Service</h3>
<table>
    <tr>
        <td>Type Company Name: </td>
        <td>
            <div class="ui-widget" style="text-align:left">
                    <asp:TextBox ID="txtCompanyName" runat="server" Width="350px" CssClass="textboxAuto"  Font-Size="12px" />
            </div>
        </td>
    </tr>        
</table>

JS Code 

<link rel="stylesheet" href="http://code.jquery.com/ui/1.10.3/themes/smoothness/jquery-ui.css">
<script src="http://code.jquery.com/jquery-1.9.1.js"></script>
<script src="http://code.jquery.com/ui/1.10.3/jquery-ui.js"></script>
<script language="javascript" type="text/javascript">
    $(function () {
        $('#<%=txtCompanyName.ClientID%>').autocomplete({
    source: function (request, response) {
        $.ajax({
            url: "Default.aspx/GetCompanyName",
            data: "{ 'pre':'" + request.term + "'}",
            dataType: "json",
            type: "POST",
            contentType: "application/json; charset=utf-8",
            success: function (data) {
                response($.map(data.d, function (item) {
                    return { value: item }
                }))
            },
            error: function (XMLHttpRequest, textStatus, errorThrown) {
                alert(textStatus);
            }
        });
    }
});
});
</script>

Step-6: Write a function for fetch data from database and show in Autocomplete TextBox.

[WebMethod]
[ScriptMethod(ResponseFormat= ResponseFormat.Json)]
public static List<string> GetCompanyName(string pre)
{
    List<string> allCompanyName = new List<string>();
    using (MyDatabaseEntities dc = new MyDatabaseEntities())
    {
        allCompanyName = (from a in dc.TopCompanies
                            where a.CompanyName.StartsWith(pre)
                            select a.CompanyName).ToList();
    }
    return allCompanyName;
}

Step-7: Run Application