Replace Href Several Strings In Asp.net?

I need to find several hrefs in html like this:

<table>
<tr><td><a href="url1">link1</a></td>
<td><a href="url2"><img src="image.jpg" /></a></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><a href="url1?ID=1">link1</a></td>
<td><a href="url2?ID=1"><img src="image.jpg" /></a></td>
</tr>
</table>