getting Domain Base Url from a server

See more:

C#

ASP.NET

C#4.0

I have pointed out 2 url for my application server, which means user can login with any of that url
(Say for an example user can browse with www.xxx.com and www.yyy.com).
Now, i have a problem with getting base URL from my server.

Early we have used only one domain url say www.xxx.com,that time i dont have any problem to get base URL.

When ever i got base URL through code,it gives right base URL www.xxx.com.

But after pointing out with two URL's, we got problem to get base URL's

For example

When i try to get base url through code, when my browser url is www.xxx.com. The base url will be www.xxx.com

When i try to get base url through code, when my browser url is www.yyy.com. The base URL will be www.xxx.com only... but my base url should be www.yyy.com

Please help me to get right base url through the C# code.



thanks and regards
Arun R