I am trying to make my first AJAX Control and I get error. I probbly missed some steps but I cann't find them eventhough I read many tutorials, probbly since I am new in AJAX, so I need to be guided step-by-step.

These are the steps I've already done:

1. Downloading AJAX ToolKit.
2. Adding These Controls to the ToolBox.
3. creating new ASP.NET Website (I heard about AJAX-Enabled Option, but I dont have this option)
4. Adding a AJAX Tool.

And thats it.

I read that I need to register add AjaxControlToolkit.dll in application bin folder, but I dont know how to do that and I dont have Bin Folder in my website, only App_Data Folder.

than I need to add this to the web config:

<add tagPrefix="ajaxToolkit" namespace="AjaxControlToolkit" assembly="AjaxControlToolkit"/>

than I need to add this to my website:

 <asp:ScriptManager ID="scriptmanager1" EnablePartialRendering="true" runat="Server" /> 

This is the error I receive:

"Compilation Error Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.

Compiler Error Message: CS0012: The type 'System.Web.UI.ExtenderControl' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'."

Source Error:

Line 16:         <br />
Line 17:         <asp:Label ID="Label1" runat="server" Text="Label" Width="229px"></asp:Label><br />
Line 18:         <asp:ConfirmButtonExtender ID="ConfirmButtonExtender1" runat="server" ConfirmText="are you sure"
Line 19:             TargetControlID="Button1">
Line 20:         </asp:ConfirmButtonExtender>

Does anyone know how can I solve this error?