How to perform sum of all cells using linq and bind to grid

Hi,
you can get result by union.
try

if my class is
public class DataTest
{
    public string Sname { get; set; }
    public int Marks { get; set; }
    public int Percentage { get; set; }
}

//and i have some dummy data like

List dataTest = new List();
dataTest.Add(new DataTest { Sname = "aa", Marks = 50, Percentage = 50 });
dataTest.Add(new DataTest { Sname = "aa", Marks = 60, Percentage = 60 });
dataTest.Add(new DataTest { Sname = "bb", Marks = 80, Percentage = 80 });
dataTest.Add(new DataTest { Sname = "bb", Marks = 60, Percentage = 60 });

//now get sum of mark and average of percentage.

List mrksbrpby = (from n in dataTest
                                        group n by new { n.Sname } into grp
                            orderby grp.Key.Sname
                            select new DataTest
                                        {
                                            Sname = grp.Key.Sname,
                                            Marks = grp.Sum(mark=>mark.Marks),
                                            Percentage = Convert.ToInt32(grp.Average(per => per.Percentage)),
                                        }).ToList();

//now merge it with original list

dataTest = dataTest.Union(mrksbrpby).OrderBy(t => t.Sname).ToList();

hope this will help you.