Add this extension method to your code:
public static Uri UrlOriginal(this HttpRequestBase request)
{
string hostHeader = request.Headers["host"];
return new Uri(string.Format("{0}://{1}{2}",
request.Url.Scheme,
hostHeader,
request.RawUrl));
}
And then you can execute it off the RequestContext.HttpContext.Request property.
There is a bug (can be side-stepped, see below) in Asp.Net that arises on machines that use ports other than port 80 for the local website (a big issue if internal web sites are published via load-balancing on virtual IP and ports are used internally for publishing rules) whereby Asp.Net will always add the port on the AbsoluteUri property - even if the original request does not use it.
This code ensures that the returned url is always equal to the Url the browser originally requested (including the port - as it would be included in the host header) before any load-balancing etc takes place.
At least, it does in our (rather convoluted!) environment :)
If there are any funky proxies in between that rewrite the host header, then this won't work either.
Update 30th July 2013
As mentioned by @KevinJones in comments below - the setting I mention in the next section has been documented here: http://msdn.microsoft.com/en-us/library/hh975440.aspx
Although I have to say I couldn't get it work when I tried it - but that could just be me making a typo or something.
Update 9th July 2012
I came across this a little while ago, and meant to update this answer, but never did. When an upvote just came in on this answer I thought I should do it now.
The 'bug' I mention in Asp.Net can be be controlled with an apparently undocumented appSettings value - called 'aspnet:UseHostHeaderForRequest' - i.e:
<appSettings>
<add key="aspnet:UseHostHeaderForRequest" value="true" />
</appSettings>
I came across this while looking at HttpRequest.Url in ILSpy - indicated by the ---> on the left of the following copy/paste from that ILSpy view:
public Uri Url
{
get
{
if (this._url == null && this._wr != null)
{
string text = this.QueryStringText;
if (!string.IsNullOrEmpty(text))
{
text = "?" + HttpEncoder.CollapsePercentUFromStringInternal(text,
this.QueryStringEncoding);
}
---> if (AppSettings.UseHostHeaderForRequestUrl)
{
string knownRequestHeader = this._wr.GetKnownRequestHeader(28);
try
{
if (!string.IsNullOrEmpty(knownRequestHeader))
{
this._url = new Uri(string.Concat(new string[]
{
this._wr.GetProtocol(),
"://",
knownRequestHeader,
this.Path,
text
}));
}
}
catch (UriFormatException)
{ }
}
if (this._url == null) { /* build from server name and port */
...
I personally haven't used it - it's undocumented and so therefore not guaranteed to stick around - however it might do the same thing that I mention above. To increase relevancy in search results - and to acknowledge somebody else who seeems to have discovered this - the 'aspnet:UseHostHeaderForRequest' setting has also been mentioned by Nick Aceves on Twitter