Question

I have a multiline textbox in which I should not allow the user to enter any HREF links.
So I am trying to string match using Regex as follows.
But I am not getting the error message. What am I doing wrong?

Regex strMatch = new Regex(@"^(?:(?:<a )?href|</a>)", RegexOptions.Compiled | RegexOptions.IgnoreCase);
if (strMatch.IsMatch(EmailTextBox.Text.Trim()))
 {
   vsumPage.AddErrorMessage("Cannot enter links");
 }

Also the same check needs to work in JS too. But it it giving me some exception. not sure what am i doing wrong. Here is my JS function

function doPreview()
 {
  var getEncodedStr = encode("<%=EmailTextBox.ClientID%>"); 
  var strInvalid = "Email instructions cannot have links included";
  var str = getEncodedStr.match(/@"(?:<a )?href|</a>"/) ;
  if (str == null)
  {
    var targetURL = 'Preview.aspx?txtName=' + getEncodedStr ;
    window.open(targetURL, null, "height=700,width=600,dependent=yes,hotkey=no,menubar=no,resizable=yes,scrollbars=yes,status=no,titlebar=no,toolbar=no");
    return false;
  }
  else
  {
   alert(strInvalid);
  }
}

Here’s the output that I am testing it with

Testing Testing <br/>
<b> Hello Testing </b> <br/>
<b> Testing 2000 character and link check </b> <br/>
<b> Hello </b> <a href="www.google.com">Click Me </a>

Updated again:
Tried this one as given below:
But it always comes to the alert “Test3 0” part…even when an

          function doPreview()
      {
          var getEncodedStr = encode("<%=EmailTextBox.ClientID%>"); 
          var strInvalid = "Email instructions cannot have links included";
          var checkCount = "0" ;
          alert("Test 1" + checkCount);
          if(/<\/[\s\S]?a\b/gm.test(decode(getEncodedStr)))
          { 
            checkCount = "1" ;
            alert("Test 2" + checkCount);
            alert((/<\/?a\b/.test(decode(getEncodedStr))));
            return false;
          }
          if (checkCount == "0")
          {                  
            alert("Test 3" + checkCount);
            var targetURL = 'EPreview.aspx?txtName=' + getEncodedStr ;
            window.open(targetURL, null, "height=700,width=600,dependent=yes,hotkey=no,menubar=no,resizable=yes,scrollbars=yes,status=no,titlebar=no,toolbar=no");
            return false;
          }
      }

Answer 1

The ^ asserts that this pattern occurs at the beginning of the string. Try removing it. Also you could probably change the pattern to:

@"</?a\b"

This will simply look for a <a or </a making sure that it is really an anchor tag, by using the word-boundary \b (which asserts that there is no letter or digit or underscore afterwards – but a space or > for example).

If that does not do it, it would really help to see your actual input.