try this
string xmlval = "<@>asdfsadfsadf</@>";
string descriptval = xmlval.Substring(xmlval.LastIndexOf("<@>"));
string findfrom = "<@>";
string findto = "</@>";
int start = descriptval.IndexOf(findfrom);
int to = descriptval.IndexOf(findto, start + findfrom.Length);
if (start < 0 || to < 0)
return;
else
msg = descriptval.Substring(start + findfrom.Length, to - start - findfrom.Length);
Console.WriteLine(msg);
Console.ReadLine();