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Editorial Team
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Asked: 2026-05-23T23:34:24+00:00

I have the following so far: ^((http[s]?|ftp):\/\/)(([^.:\/\s]*)[\.]([^:\/\s]+))(:([^\/]*))?(((\/\w+)*\/)([\w\-\.]+[^#?\s]+)(\?([^#]*))?(#(.*))?)?$ Been testing against these: https://www.google.com.ar:8080/dir/1/2/search.html?arg=0-a&arg1=1-b&arg3-c#hash https://google.com.ar:8080/dir/1/2/search.html?arg=0-a&arg1=1-b&arg3-c#hash https://google.com:8080/dir/1/2/search.html?arg=0-a&arg1=1-b&arg3-c#hash

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I have the following so far:

^((http[s]?|ftp):\/\/)(([^.:\/\s]*)[\.]([^:\/\s]+))(:([^\/]*))?(((\/\w+)*\/)([\w\-\.]+[^#?\s]+)(\?([^#]*))?(#(.*))?)?$

Been testing against these:

https://www.google.com.ar:8080/dir/1/2/search.html?arg=0-a&arg1=1-b&arg3-c#hash 
https://google.com.ar:8080/dir/1/2/search.html?arg=0-a&arg1=1-b&arg3-c#hash 
https://google.com:8080/dir/1/2/search.html?arg=0-a&arg1=1-b&arg3-c#hash 
http://www.foo.com
http://www.foo.com/
http://blog.foo.com/
http://blog.foo.com.ar/
http://foo.com
http://blog.foo.com
http://foo.com.ar

I’m using the following tool to test the regexes: regex tester

So far I’ve been able to yield the following groups:

  1. full protocol
  2. reduced protocol
  3. full domain name
  4. subdomain?
  5. top level domain
  6. port
  7. port number
  8. rest of the url
  9. rest of the “directory”
  10. no idea how to drop this group
  11. page name
  12. argument string
  13. argument string
  14. hash tag
  15. hash tag

I will be using this regex to change the subdomain for my application for cross-domain redirect hyperlinks.

Using Request.Url as a parameter, I want to redirect from

http://example.com or http://www.example.com to http://blog.example.com

How can I achieve this?

I can’t really tell what, if any, the current subdomain ( either nothing, www, blog, or forum, for instance) actually is…

What would be the best way to make this replacement?

What I actually need is some way to find out what the top level domain is. in either http://www.example.com, http://blog.example.com, or http://example.com I want to get example.com.

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1 Answer

  1. Editorial Team

    What would be the best way to make this replacement?

    This may not be the answer you’re looking for… but IMO the best way would be to make use of the System.Uri class.

    The Uri class will easily extract the Host for you – and you can then split the host on “.” delimiter – that should easily give you access to the current subdomain.

    This is just my opinion – and its especially formed because I find it hard to maintain regex code like ^((http[s]?|ftp):\/\/)(([^.:\/\s]*)[\.]([^:\/\s]+))(:([^\/]*))?(((\/\w+)*\/)([\w\-\.]+[^#?\s]+)(\?([^#]*))?(#(.*))?)?$

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