The Server.MapPath
method returns a file system path. What you want is a (relative) URL. Paths and URLs are completely different things. Typically, you need a path if you want to manage files in your server side code, and you need a URL is you are providing access to those files to visitors via hyperlinks. URLs can be constructed from strings:
var url = string.Format("/Images/Property/{0}/{1}", rProprtyId, filename)