1. Create a clone of the data in the above table that you have.
2. Specify the Data Type in clone table, for the sort column as needed. Eg. System.Decimal for decimal column.
3. Import each row from original table to clone table.
4. Commit the changes in clone table.
5. Create a DataView on clone table.
6. Specify the sort column and sort order for the DataView.
7. Bind DataView to GridView.
DataTable dtMarks1 = dtMarks.Clone();
dtMarks1.Columns["Total"].DataType = Type.GetType("System.Decimal");
foreach (DataRow dr in dtMarks.Rows)
{
dtMarks1.ImportRow(dr);
}
dtMarks1.AcceptChanges();
DataView dv = dtMarks1.DefaultView;
dv.Sort = "Total DESC";
GridView1.DataSource = dv;
GridView1.DataBind();