1-) C# DEVEXPRESS RMOS - Gridview runtime add column ekleme

  bool varmi = false;

                foreach (GridColumn item in gridView11.Columns)

                {

                    if (item.FieldName.Equals("Servis Payı"))

                    {

                        varmi = true;

                    }

                }

                if (varmi == false) gridView11.Columns.AddVisible("Servis Payı");

kaynak  : https://docs.devexpress.com/WindowsForms/3483/controls-and-libraries/data-grid/views/grid-view/columns

ayrıca datatableye eklemek için -> dt.Columns.Add("Servis Payı", typeof(string));