finally i did this after googling
XDocument xmlProducts = XDocument.Parse(results);
var student = from stu in xmlProducts.Descendants("Students")
select new Students
{
StudentName = stu.Element("StudentName").Value,
RegNo = Convert.ToInt32(stu.Element("RegNo").Value),
Marks1 = Convert.ToInt32(stu.Element("Marks1").Value),
Marks2 = Convert.ToInt32(stu.Element("Marks1").Value),
Marks3 = Convert.ToInt32(stu.Element("Marks1").Value),
Marks4 = Convert.ToInt32(stu.Element("Marks1").Value)
};
dataGrid4.ItemsSource = student;