How to get target URL?

I'm writing an application which extracts image files from .css. First I scan the HTML file to extract all .css files:

In HTML I have something like this:

<link rel="stylesheet" type="text/css" media="screen" href="TemplatesFBL/Styles/screen.css" />

www.mysite.com/Templates/Styles/screen.css is my first target link.

Inside that file I may have something like this:

background-image:url('../Images/CssImg/pageShadowSides.gif');

The question is, how can I combine www.mysite.c开发者_StackOverflow中文版om/Templates/Styles and ../Images/CssImg/pageShadowSides.gif in order to get www.mysite.com/Templates/Images/CssImg/pageShadowSite.gif?

Can I use some built-in function or do I have to write my own?

Any help would be greatly appreciated!

You're looking for the Uri class.

Store a Uri for the base URL, then create a new Uri with a relative path:

var baseUri = new Uri("http://www.mysite.com/Templates/Styles/screen.css", UriKind.Absolute);
var fullUri = new Uri(baseUri, "../Images/CssImg/pageShadowSides.gif");

Note that the CSS filename should be included in the URL.
Since it doesn't end in a slash, the Uri parser will realize that it's a filename and behave correctly.