Question: I'm wondering if it is possible to use the OpenCV framework to recognise a building? 
For example, if I store an image of a building, is it possible to use OpenCV to detect this building through the iPhone camera?

Thanks!

Answer: 
You need to use **Ajax Control Tool kit's Cascaded Drop-down**

Here is the like for it:

<http://www.asp.net/AjaxLibrary/AjaxControlToolkitSampleSite/Walkthrough/CCDWithDB.aspx>

and here is the demo:

<http://www.asp.net/AjaxLibrary/AjaxControlToolkitSampleSite/CascadingDropDown/CascadingDropDown.aspx>

here is a tutorial link:

<http://www.dotnetfox.com/articles/ajax-cascading-dropdown-example-with-database-in-Asp-Net-1078.aspx>

Hope this material helps.
You should try to use PageMethods in JS to load the dropdowns any way you like any time you like.