Dynamically Generated HTML In C# To Be Formatted?

I have an ASP.NET web forms site with a rather large menu. The HTML for the menu is dynamically generated via a method in the C# as a string. I.e., what is being returned is something like this:

<ul><li><a href='default.aspx?param=1&anotherparam=2'>LINK</a></li></ul>

Except it is a lot bigger, and the lists are nested up to 4 deep.

This is written to the page via a code block.

However, instead of returning a flat string from the method I would like to return it as formatted HTML, so when rendered it looks like this:

<ul>
<li>
<a href='default.aspx?param=1&anotherparam=2'>LINK</a>
</li>
</ul>

I thought about loading the html into an XmlDocument but it doesn't like the & character found in the query strings.