12 replies
Thanks for everyone who helped me with the first problem but I have one more. I need to validate that a url is typed into the text box before a user clicks on the button to send the url to the webbrowser control.

basically I need it to do this....

When a user types in the complete url http://www.yoursite.com and then hits the go button it will take them to the url. But if they type in anything but a valid url I want it to display a message box and preventing them from visiting a page. If anyone types in anything but a valid url the program will crash. How do I validate that it is a valid url and not garbage.

#url #valadating
  • Profile picture of the author jwlnewsome
    Hi, try pinging the url before you preform the action. There are a few php scripts out there that can ping addresses to see if there is a response. I would personally cURL the url to see if i get anything back other than a 404 error
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  • Profile picture of the author NicheExposed
    i am working in vb.net writing an exe program. I am using a webbrowser control, text box and a button.

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  • Profile picture of the author warmlikecoffee
    You can do something like this:

    If Texbox1.Text.Substring(0,7) = "hxxp://" Or Textbox1.Text.Substring(0, 4) = "wwvv." Then
    MessageBox.Show("This is a URL")
    End If

    The code checks the first letters of your Textbox1, if it begins with hxxp:// or wwvv. then it is deemed as a valid URL.

    If you need more help just let me know, I can help when I have free time.

    Change the xx to tt and vv to w, the forum wouldn't let me post a link due to my post count.
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    • Profile picture of the author Mike P Smith
      If you really want a challenge (and earn your geek stripes) try using "Regular Expressions" - I think there are libraries available for VB.NET if that is your platform.

      That can validate a URL rather well with just one statement.

      Mike Smith
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  • Profile picture of the author Johnathan
    Although I`m not too familiar with vb.net, I`m assuming its similar to VB6. Simply navigate to the URL, and if nothing is there, then you know its not valid. I.e., webbrowser1.navigate \"whatever.com\" then check the \'location\' attribute, etc.
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  • Profile picture of the author NicheExposed
    I ended up calling a programming friend of mine who gave me the code. I had to create a function. here is the code if anyone else needs it.

    PrivateFunction UrlIsValid(ByVal url AsString) AsBoolean
    Dim is_valid AsBoolean = False
    If url.ToLower().StartsWith("www.") Then url = _
    "http://" & url
    Dim web_response As HttpWebResponse = Nothing
    Dim web_request As HttpWebRequest = _
    web_response = _
    DirectCast(web_request.GetResponse(), _
    Catch ex As Exception
    IfNot (web_response IsNothing) Then _

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  • Profile picture of the author mywebwork
    Originally Posted by NicheExposed View Post

    If anyone types in anything but a valid url the program will crash.
    Just a thought, you might consider writing an Error Handler as well - having the program crash if it receives a bad URL is not particularly user-friendly!

    Keep in mind that the user may enter a valid URL by clicking on an invalid hyperlink within a web page. That bad URL will probably make it past your URL format check.

    Beat of luck with your project...

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  • Profile picture of the author NicheExposed
    when someone clicks on a link in a web page that is bad will just return a page can not be displated error. That has nothing to do with the coding problem within the software.

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  • Profile picture of the author AndyBlackSEO
    For php you would use regex (regular expression) to determine whether a url is in a valid format. You could then go one further by using cURL to grab the contents of the page and verify that a valid live webpage exists at the end of it. I'm creating this functionality for my latest product and it works perfectly.

    What platform are you wanting to code this in? web app or a windows application?
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  • Profile picture of the author Gimme4Free

    PHP Code:
    function url_exists()
    VAR1   curl_init();
        if (
    false === VAR1)
    curl_setopt(VAR1CURLOPT_HTTPHEADER, Array("User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv: Gecko/20080623 Firefox/") );
    VAR2  curl_exec(VAR1);
        if (
    preg_match('/200 OK/i',substr_replace(VAR2,'',30))) {
    Replace VAR1 with $ something and VAR2 with $ something else (WF wont let me post up proper variables)
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  • Profile picture of the author sanjid112
    You can try this regex.

    CODE-one linear ($urlregex):
    PHP Code:
    if (
    eregi(, )) {echo "good";} else {echo "bad";} 
    (OPTIONAL: Read more for some explanations

    it will validates all this type of url ($url)
    PHP Code:
    // valid urls 
    "http://somewhere.com/index.html/";  //this is valid!! 
    The CODE-broken into section for easy editing and understanding ($urlregex):
    PHP Code:
    // SCHEME 

    // USER AND PASS (optional) 
    .= "([a-z0-9+!*(),;?&=.-]+(:[a-z0-9+!*(),;?&=.-]+)?@)?"

    .= "[a-z0-9+-]+(.[a-z0-9+-]+)*";  // http://x = allowed (ex. http://localhost, http://routerlogin) 
    // .= "[a-z0-9+-]+(.[a-z0-9+-]+)+";  // http://x.x = minimum 
    // .= "([a-z0-9+-]+.)*[a-z0-9+-]{2,3}";  // http://x.xx(x) = minimum 
    //use only one of the above 

    // PORT (optional) 
    .= "(:[0-9]{2,5})?"
    // PATH  (optional) 
    .= "(/([a-z0-9+-].?)+)*/?"
    // GET Query (optional) 
    .= "(?[a-z+&.-][a-z0-9;:@/&%=+.-]*)?"
    // ANCHOR (optional) 
    .= "(#[a-z_.-][a-z0-9+.-]*)?$"

    // check 
    if (eregi(, )) {echo "good";} else {echo "bad";} 
    All the lines can be safely removed (except for the hostname) if you do not want allowing some URL segment (if you don't want getqueries in your urls, just comment the respective $urlregex .= ....) - but do not reorder them.
    the "(optional)" states that the part MAY exist, but url will be valid even if it doesn't contain the part (see the valid urls above).

    <http[s]|ftp> :// [user[:pass]@] hostname [port] [/path] [?getquery] [anchor]
    • take into account allowed safe characters
    • assumption .. (double dot) is never allowed in hostname or path.


    PS. please tell me if it is wrong to paste the code here. and wait for some feedbacks
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    • Profile picture of the author Mike P Smith
      Nice post, sanjid112.

      For VB.NET, using sanjid112's regex, this is what you need:

      If Not Regex.IsMatch(myURL, "^(https?|ftp)://([a-z0-9+!*(),;?&=.-]+(:[a-z0-9+!*(),;?&=.-]+)?@)?[a-z0-9+-]+(.[a-z0-9+-]+)*(:[0-9]{2,5})?(/([a-z0-9+-].?)+)*/?(?[a-z+&.-][a-z0-9;:@/&%=+.-]*)?(#[a-z_.-][a-z0-9+.-]*)?$")Then
      ' write your error code
      ' here.
      ' write your success code here
      End If

      Mike Smith
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