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Text box which allows only certain html tags

Posted on 2008-10-29
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Last Modified: 2013-12-17
I have a text box (multi line) on my aspx page.  This field needs to support only certain html tags (<B>.<U> and <i> and remove all other tags.  The code-behind is C#.  Any help with examples would be appreciated.


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Question by:Kiran_M
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8 Comments
 

Expert Comment

by:wolfdood
ID: 22831496
You could use the replace method.  For example... Replace("your string here", " <br />", "")
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Author Comment

by:Kiran_M
ID: 22831584
Hmm...that was my first approach. How do i say ..replace all html tags in the string except ( tagA, TagB, Tag C).
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Expert Comment

by:wolfdood
ID: 22831672
How about this?
Function stripHTML(ByVal strHTML)

        'Strips the HTML tags from strHTML using split and join
 

        'Ensure that strHTML contains something

        If len(strHTML) = 0 Then

            stripHTML = strHTML

            Exit Function

        End If
 

        Dim arysplit, i, j, strOutput
 

        arysplit = split(strHTML, "<")
 

        'Assuming strHTML is nonempty, we want to start iterating

        'from the 2nd array postition

        If len(arysplit(0)) > 0 Then j = 1 Else j = 0
 

        'Loop through each instance of the array

        For i = j To ubound(arysplit)

            'Do we find a matching > sign?

            If instr(arysplit(i), ">") Then

                'If so, snip out all the text between the start of the string

                'and the > sign

                arysplit(i) = mid(arysplit(i), instr(arysplit(i), ">") + 1)

            Else

                arysplit(i) = "<" & arysplit(i)

            End If

        Next
 

        'Rejoin the array into a single string

        strOutput = join(arysplit, "")
 

        'Snip out the first <

        strOutput = mid(strOutput, 2 - j)
 

        'Convert < and > to &lt; and &gt;

        strOutput = replace(strOutput, ">", "&gt;")

        strOutput = replace(strOutput, "<", "&lt;")
 

        stripHTML = strOutput

    End Function

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Expert Comment

by:wolfdood
ID: 22831709
Sorry, forgot to add when looping through each instance of the array just check for the tags you dont; want to remove.
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Author Comment

by:Kiran_M
ID: 22831801
I came across this code online. However this strips all html tags. Let me try fine tuning this  code to ignore certain tags. Do you have C# equivalent?  Thanks.

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Assisted Solution

by:wolfdood
wolfdood earned 250 total points
ID: 22831894
Sorry, i only have the VB. Try using http://www.developerfusion.com/tools/convert/vb-to-csharp/ to convert it.
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Author Comment

by:Kiran_M
ID: 22832084
Thank you. I'll give it a try and get back.
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Accepted Solution

by:
Kiran_M earned 0 total points
ID: 22999320
Woolfdood, the code convertor did a very poor job. I am having trouble changing the converted C# code to work. Basically i  need to check all the tags entered in the text and if it is not one of the allowed html tags, I need to throw an error message.

Got any other ideas?
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