user controls - Best practice in building outlook layout in asp.NET & telerik radpanelbar as a page arch? -

I am working on the enterprise app, I am using teleic control to make life easier;) on the left side The layout of my application is used for the navigation menu, the content is on the right.

I want to navigate this Navigation menu on a UserTrock (.ascx file) instead of a page (.aspx file) in the Navigation Control Master page I have several reasons to do this type of navigation :

1. I have many user controls, and I do not want to create as many pages (.aspx) as many user controls I have.
2. Most importantly, I want to do it with Post Pack (AJX) on the fly.

   So anyone can tell about the best practice to do this.

   The navigation user control program may have to be loaded through AJAX when the user has a panel item Clicks on. Still, the user's control over the master page and the loading position from the content page is awkward for me and I personally do not accept it as a good architectural decision.