DataTable DTable = new DataTable("Table1");
            for (int i = 0; i < dgvOrder.ColumnCount; i++)
                DTable.Columns.Add(new DataColumn(dgvOrder.Columns[i].Name));
            foreach (DataGridViewRow item in this.dgvOrder.Rows)
                {
                    DataRow dr = DTable.NewRow();
                    if (item.DataBoundItem != null)
                    {
                        dr = (DataRow)((DataRowView)item.DataBoundItem).Row;
                        DTable.ImportRow(dr);
                    }
                }
            System.IO.FileStream stream = new System.IO.FileStream("exam.xml", System.IO.FileMode.Create);
            System.Xml.XmlTextWriter xmlWriter = new System.Xml.XmlTextWriter(stream, Encoding.Unicode);
            DTable.WriteXml(xmlWriter);