What is the process behind __doPostback generating a URL on an ASP.NET website?

Can you please check out the following URL:

When you select "Exhibitor A to Z" from the dropdown menu and click search, a javascript function is triggered for each link (

javascript:__doPostBack('ctl00$MainContent$grdExhList$ctl00$ctl04$lnkExhLink','')
) which generates a unique URL in the browser.

For instance, 

https://www.event-reg.biz/oem-Koelnmesse/OnlineExh?e=/v5urzZW/hm8SuWqRTOYlg==&p=https%3a%2f%2fwww.event-reg.biz%2foem-Koelnmesse%2fOnlineExhListing
is an example of the resulting URL from the mentioned Javascript function call.

I have tried looking into the __doPostBack function but couldn't find much information. Any advice or assistance on this matter would be greatly appreciated.

Thank you kindly in advance.

javascriptasp.netdopostback

Answer №1

Chronological sequence of actions:

  1. When a link is clicked on the client's side, it triggers the execution of the __doPostBack method causing a POST request to be sent to the following URL: "". This request includes various key/value pairs, with one being "__EVENTTARGET" set to "ctl00$MainContent$grdExhList$ctl00$ctl04$lnkExhLink". Upon receiving this request, the server responds back to the client with the following message: "1|#||4|157|pageRedirect||%2foem-Koelnmesse%2fOnlineExh.aspx%3fe%3d%2fv5urzZW%2fhm8SuWqRTOYlg%3d%3d%26p%3dhttps%253a%252f%252fwww.event-reg.biz%252foem-Koelnmesse%252fOnlineExhListing|"
  2. The client then proceeds to send a GET request to the URL provided in the previous POST response, which translates to: "%2foem-Koelnmesse%2fOnlineExh.aspx%3fe%3d%2fv5urzZW%2fhm8SuWqRTOYlg%3d%3d%26p%3dhttps%253a%252f%252fwww.event-reg.biz%252foem-Koelnmesse%252fOnlineExhListing", and can further be decoded to "/oem-Koelnmesse/OnlineExh.aspx?e=/v5urzZW/hm8SuWqRTOYlg==&p=https%3a%2f%2fwww.event-reg.biz%2foem-Koelnmesse%2fOnlineExhListing"
  3. This URL "/oem-Koelnmesse/OnlineExh.aspx?e=/v5urzZW/hm8SuWqRTOYlg==&p=https%3a%2f%2fwww.event-reg.biz%2foem-Koelnmesse%2fOnlineExhListing" undergoes a redirection at the server level to: "/oem-Koelnmesse/OnlineExh?e=/v5urzZW/hm8SuWqRTOYlg==&p=https%3a%2f%2fwww.event-reg.biz%2foem-Koelnmesse%2fOnlineExhListing", ultimately leading to the final displayed URL in the browser.


If you wish to visually understand this process more clearly, you can use tools such as Fiddler to intercept the network traffic and observe it firsthand:
https://i.sstatic.net/pCfQZ.png

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