Replace href several strings in vb.net asp.net - asp.net

Question

I need to find several hrefs in html like this:
<table>
<tr><td>link1</td>
<td><img src="image.jpg" /></td>
</tr>
</table>
Once found I need to add (replace) to each href something like this:
?ID=1
therefore the html should turn out like this:
<table>
<tr><td>link1</td>
<td><img src="image.jpg" /></td>
</tr>
</table>
Any help would be appreciated, thanks, Mike.

Answer 1

Here's the new code:
Shared Function AdjustURL(ByVal psInput As String, ByVal psAppend As String) As String
Dim sOrig As String = " " & psInput 'Prepending a space (browser will ignore) in case the first character is a link.
Dim sOutput As String = ""
Dim iEnd As Integer = -1, iQuestion As Integer = -1
While sOrig.Length > 0
sOutput &= sOrig.Substring(0, 1)
sOrig = sOrig.Substring(1)
iEnd = -1
If sOrig.StartsWith("<a href=") Then 'Is this a safe assumption, what if it's not an <a> or href isn't next after only one space?
If sOrig.StartsWith("<a href=""") Then
iEnd = InStr(10, sOrig, """") 'URL ends with a Quote
Else
iEnd = InStr(9, sOrig, " ") 'URL ends with a Space - are there other possibilities?
End If
iQuestion = InStr(sOrig, "?")
If iQuestion > iEnd Then iQuestion = -1
sOutput &= sOrig.Substring(0, iEnd - 1) & IIf(iQuestion > -1, "?", "&") & psAppend
sOrig = sOrig.Substring(iEnd - 1)
End If
End While
Return sOutput
End Function
Call:
Dim sHTML As String = "<table> <tr><td>link1</td> <td><img src=""image.jpg"" /></td> </tr> </table>"
Response.Write(Class1.AdjustURL(sHTML, "ID=1"))
Result:
<table> <tr><td>link1</td> <td><img src="image.jpg" /></td> </tr> </table>
I'm sure there will be other replacements you will discover over time as users enter things. I'd definitely recommend replacing <script with something like <span style=display:none to avoid javascript injection. You'll also want to be sure to avoid SQL injection before writing this to your database.