It is not possible. The AF Treeview control is designed for Windows Form use only.
@Fernando: The AFTreeView class inherits from the TreeView one which is a Windows form only component. Although, nothing prevents you to write your own one if you have enough time.
Can you elaborate more on your use case? We have many products and data access products that have connectivity with PI AF that can surely help you.
If you decide to take the time to implement this, I have a few pointers.
If you start with the component System.Web.UI.WebControls.TreeView, you can take it pretty far untill you notice that when it comes to AJAX capabilities this is pretty useless.
Then you'll need to download "The CSS Friendly Control Adapters kit" from cssfriendly.codeplex.com and make use of the TreeViewAdapter.cs file, to "AJAX enable" the component.
Third step would obviously be getting data into the component, and that wouldn't be too much of a hassle if you've used the AF SDK before.
Are you required to go ASP.net only, or can you possibly use Sharepoint to host your page? If so, you can use the PI TreeView webpart to provide the data you need, out of the box.
If you're not using Sharepoint in your intranet pages (I assume it's intranet), you'll most likely have the free version of Sharepoint (either Windows Sharepoint Services 3.0 or Sharepoint Foundation 2010) included with some Windows server you're using. If you set it up you can host PI Webparts there, and bring them into your ASP.net page using the iframe functionality of html. I have described this process thoroughly in my blog post here: vcampus.osisoft.com/.../using-pi-webparts-in-non-sharepoint-environments.aspx
And also, if my memory serves me right, there is a new AF data webpart in the PI Webparts 2012 product, due to be released in Q4. I did see it in the product demo in the vCampus conference last year, but I'm not 100% sure how it differs from the AF data you can see in the PI TreeView webpart.
Maybe someone can tell us more about this?