Building a ASP.NET Web Project

1. From the Visual Studio 2010 File menu select New | Web Site.
2. Select the "ASP.NET Web Site" and enter a name and location path.
   

Integrating ComboBox Control to Web Page

1. Drag and drop an AjaxPanel component from the Toolbox to target web page.
2. Drag and drop the combobox component from the Toolbox to that AjaxPanel.

Setting Properties of ComboBox

1. Click the ComboBox's SmartTag in the Design View of the default web page.
   
2. To modify and edit the combobox, please click the Edit Item. After the clicking, you will see a property window called Item Editor.
3. Click the Add item icon in the upper left corner. A new ComboBoxItem appears in the item builder.
   
4. Set the Text property to "1". Add left items in the same way.
5. Press OK to close the ComboBox Item Builder.
6. Back in the Smart Tag, choose a Skin from the drop-down control.
   

Now the building of a simple combobox has finished. And the image attached below is used to represent the final result of above ASP.NET AJAX combobox creating application.