It is very simple, there are many ways to do this, but basically you use asp.net vb code that outputs HTML and / or even some JavaScript many ways to do this, simplified:
Response.Write("<div class='mymenu'>")
Response.Write("<ul>")
Response.Write("<li>Menu Item 1</li>")
Response.Write("<li>Menu Item 2</li>")
Response.Write("<li>Menu Item 3</li>")
Response.Write("<li>Menu Item 4</li>")
Response.Write("</ul>")
Response.Write("</div>")
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