Development asp.NET novice help

I'm a complete novice at asp/asp.NET and am trying to edit a script so that it'll link to itself but using Request.Servervariables("URL"); so the link is created dynamicly depending on what the filename is

Code:

<% @Page Language="C#" %>
<% @Import Namespace="System.IO" %>
<%
string strDir2List = Request.QueryString.Get("dir");
string currentpage = Request.Servervariables("URL");
DirectoryInfo thisOne = null;
try
{
 thisOne = new DirectoryInfo(strDir2List);
 // Reading the directory properties
 Response.Write("<p>Creation: " + 
 thisOne.CreationTime.ToString() + "</p>");
 DirectoryInfo[] subDirectories = thisOne.GetDirectories();
 Response.Write("<ul>");
 for (int i=0; i < subDirectories.Length; i++)
 {
  Response.Write("<li><a href=\""& currentpage &"?dir=");
  Response.Write(Server.UrlEncode(subDirectories[i].FullName));
  Response.Write("\">" + subDirectories[i].Name);
  Response.Write("</a><br>");
 }
 Response.Write("</ul>");
 
 FileInfo[] theFiles = thisOne.GetFiles();
 Response.Write("<ul>");
 for (int i=0; i < theFiles.Length; i++)
 {
  Response.Write("<li><a href=\"fusen186328filecontents.jpg.aspx?file=");
  Response.Write(Server.UrlEncode(theFiles[i].FullName));
  Response.Write("\">" + theFiles[i].Name);
  Response.Write("</a><br>");
 }
 Response.Write("</ul>");
}
catch (Exception e)
{
 Response.Write("Access not possible, error: <i>");
 Response.Write(e.ToString() + "</i>");
 Response.End();
}
%>

I made the two ammendments

string currentpage = Request.Servervariables("URL");
and
Response.Write("<li><a href=\""& currentpage &"?dir=");

but it just gives me an error, any help would be much appreciated +k