How to Create a URL syntax checker in C#

How to Create a URL syntax checker in C#

• Jamie Thomson

  Hmmm... still quite vague. Could you please expound it a little more simple.
  
  I need to put it in an application (C#) and that for every url text in the textbox, when I clicked the button "GO" the url in the textbox will be check for proper syntax before the page will be loaded in my self-made browser.
  
  In regards to this, I have recently read about url conversion to its equivalence in the DNS server. I thought if I could make a program that will check a URL's ip equivalence (DNS equivalence) and would verify if its a good URL, not a spoof.
  
  Ichi
  
  
  

• AlexBB

  Hi,
  
  Is this a good means for catching URL that is not valid or URL having embedded username or redundant "www" or "http://" and the likes I am trying to catch a phish site by filtering the URL and checking its validity.
  
  Alain
  
  
  

• hawash

  1. Create a URI and determine whether the initial link is valid or rather, well formed. Check also the Query collection of the URI class and scan each key|value pair for words like "username" or "password".

  2. If it is valid then create a HTTPWEBREQUEST to grab the contents of the page.

  3. Write a validator to check whether the page contains META REFRESH or Javascript Window.Location code (Regex)

  4. If the page contains redirection then stop the request and add to a blocked list.

  5. Check the response URI (httpwebrequest class) and if it is totally different to the initial URI host property then block the URI and add to blocked list.

  6. If URI passes all checks then add to SAFE LIST.

  
  

• gorla

  I have read about an article about it.
  
  They use database. They have lists of IP addresses of well known domain names such as yahoo and google. When a certain url (maybe a spoof) attempts to navigate, the url was checked its IP equivalence and if it was found that it was different in their database, it would be possible a phish.
  
  I'm not quite sure about that but thats how I see it. =D
  
  
  

• ratslav

  U can create a java Script function onblur event of ur text box which wil validate ur URL instead of doind round trip to server
  
  

• Wil Burton

  Hi,

  you could try to create an instance of the System.Net.Uri class, if the URI is incorrect then an exception will be thrown from the constructor: http://msdn.microsoft.com/library/default.asp url=/library/en-us/cpref/html/frlrfsystemuriclassctortopic1.asp

  Mark.

  
  
  

• Juco

  what exactly does the onblur event do
  
  

• gordon LI

  yeah something like that. But I won't be using that though. Its what the article says. What I want to do is that I would try to make a program that will check the url syntax (inside the textbox) before the browser will load the page.
  
  The checking will be something like, the format of the url, if the url contains embedded usernames. or something like that.
  
  Ichi
  
  
  

• chemist

  Well wat ur telling is going to server side for validation ..

  but y to waste a server round trip

  u can simply do tat on client side .

  u can go for wat u suggested but tat would be unnecessary load on server ..n to do on client side u can do tat by using javascript

  well if u feel u want to then u tell m i wil help u out

  if u want to server side validation then u can do the way u told

  
  
  

• ahmedilyas

  this onBblur event is on text box n it is invoket wen u are out of focus

  from ur text box i.e as soon as u remove focus from textbox this event is called

  
  
  

• mexy

  U cant exactly use it in ur .cs file but u can use it as a script in ur .aspx page

  u can make javascript n use it in Head of ur .Aspx page

  the same we use javascript in Html

  
  
  

• Philip Wagenaar - Nashuatec

  Ichi_Programmer wrote:

  Hmmm... still quite vague. Could you please expound it a little more simple. I need to put it in an application (C#) and that for every url text in the textbox, when I clicked the button "GO" the url in the textbox will be check for proper syntax before the page will be loaded in my self-made browser. In regards to this, I have recently read about url conversion to its equivalence in the DNS server. I thought if I could make a program that will check a URL's ip equivalence (DNS equivalence) and would verify if its a good URL, not a spoof. Ichi

  
  
  How can you tell that from an IP address And how can you assume that the user enters (or copies) each URL into your address textbox - what about links and redirects (or did I get your paragraph wrong )
  
  

• SiTec

  javascript in C# could it be I am quite a beginner in C# and don't know that it uses JScript. :D
  
  
  

• Scott_P

  But by this u can only check for some famous URL's

  wat about rare ones ..

  
  
  
• How to Create a URL syntax checker in C#