public static void Main()
var raw = @"<?xml version=""1.0"" encoding=""utf-8""?><EMAIL> <ADDR To=""abcd@abcd.com"" Sub=""Email body""> </ADDR> <BODY>Data available at <br />{0}<br /><br />Thanks</BODY></EMAIL>";
XElement xmlMap = XElement.Parse(raw);
var url = "http://foo.bar.com";
var result = string.Format((from item in xmlMap.Elements("BODY")
select item.Value).Single(),url);
Console.WriteLine(result);