C# List<> to xml

[legi]

Calling\[code\]List<PC> _PCList = new List<PC>();...add Pc to PCList.. WriteXML<List<PC>>(_PCList, "ss.xml");\[/code\]Function\[code\]public static void WriteXML<T>(T o, string filename){ string filePath= Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData) + "\\Genweb2\\ADSnopper\\" + filename; XmlDocument xmlDoc = new XmlDocument(); XPathNavigator nav = xmlDoc.CreateNavigator(); using (XmlWriter writer = nav.AppendChild()) { XmlSerializer ser = new XmlSerializer(typeof(List<T>), new XmlRootAttribute("TheRootElementName")); ser.Serialize(writer, o); // error } File.WriteAllText(filePath,xmlDoc.InnerXml);}\[/code\]inner exception {"Unable to cast object of type 'System.Collections.Generic.List\[code\]1[PC]' to type 'System.Collections.Generic.List\[/code\]1[System.Collections.Generic.List`1[PC]]'."}Please Help