Had a requirement to throw some XML at the browser and thought this would be a useful snippet to show.
string xmlstr = @"
<statistics>
<gather>66400</gather>
<user_count>666452</user_count>
<user_demand>23.83</user_demand>
</statistics>";
Not much to it really! The key is to flush and end the response, so no interference comes from the standard asp.net output trying to offer other bits of content type.
XmlDocument doc = new XmlDocument();
doc.LoadXml(xmlstr);
Response.Clear();
Response.ContentType = "text/xml; charset=utf-8";
Response.Write(doc.OuterXml);
Response.Flush();
Response.End();