Tuesday, April 22, 2008

ASP.NET Uri Fragment is not available

Recently, a question came my way about filtering URLs that contain fragment-identifiers. A fragment-identifier goes by many different names (bookmark, pound, hash, named-anchor, etc) and is represented as a pound symbol (#) at the end of a querystring:


Unfortunately, I had looked into something similar only a few months previously, so my response came immediately: "this cannot be done." While researching a problem several months ago, I was surprised to learn that the fragment of the URL is a client-side only html tag, meaning that most modern browsers use this primarily to scroll the named element into view -- they do not transmit this information to the web server. A simple test shows this value is NEVER populated.

public partial class PageTest : System.Web.UI.Page
    protected void Page_Load(object sender, EventArgs e)
        Response.Write("Fragment = " + Request.Url.Fragment + "<br />");

Sadly, this is not ASP.NET specific. It's part of the Uri specification. A Wikipedia article on this topic suggests that you can pass "#" to the server if it is encoded as %23, although this value is treated as part of the querystring instead of being interpreted as the Uri fragment.

If you need these values in the URL, put them in the query-string.

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Unknown said...

Thank you, it was just the information I needed.