Question

So I just got my site kicked off the server today and I think this function is the culprit. Can anyone tell me what the problem is? I can’t seem to figure it out:

Public Function CleanText(ByVal str As String) As String    
'removes HTML tags and other characters that title tags and descriptions don't like
    If Not String.IsNullOrEmpty(str) Then
        'mini db of extended tags to get rid of
        Dim indexChars() As String = {"<a", "<img", "<input type=""hidden"" name=""tax""", "<input type=""hidden"" name=""handling""", "<span", "<p", "<ul", "<div", "<embed", "<object", "<param"}

        For i As Integer = 0 To indexChars.GetUpperBound(0) 'loop through indexchars array
            Dim indexOfInput As Integer = 0
            Do 'get rid of links
                indexOfInput = str.IndexOf(indexChars(i)) 'find instance of indexChar
                If indexOfInput <> -1 Then
                    Dim indexNextLeftBracket As Integer = str.IndexOf("<", indexOfInput) + 1
                    Dim indexRightBracket As Integer = str.IndexOf(">", indexOfInput) + 1
                    'check to make sure a right bracket hasn't been left off a tag
                    If indexNextLeftBracket > indexRightBracket Then 'normal case
                        str = str.Remove(indexOfInput, indexRightBracket - indexOfInput)
                    Else
                        'add the right bracket right before the next left bracket, just remove everything
                        'in the bad tag
                        str = str.Insert(indexNextLeftBracket - 1, ">")
                        indexRightBracket = str.IndexOf(">", indexOfInput) + 1
                        str = str.Remove(indexOfInput, indexRightBracket - indexOfInput)
                    End If
                End If
            Loop Until indexOfInput = -1
        Next
    End If
    Return str
End Function

Answer 1

Wouldn’t something like this be simpler? (OK, I know it’s not identical to posted code):

public string StripHTMLTags(string text)
{
    return Regex.Replace(text, @"<(.|\n)*?>", string.Empty);
}

(Conversion to VB.NET should be trivial!)

Note: if you are running this often, there are two performance improvements you can make to the Regex.

One is to use a pre-compiled expression which requires re-writing slightly.

The second is to use a non-capturing form of the regular expression; .NET regular expressions implement the (?:) syntax, which allows for grouping to be done without incurring the performance penalty of captured text being remembered as a backreference. Using this syntax, the above regular expression could be changed to:

@"<(?:.|\n)*?>"