private void BindData()
        {
            radGridView1.GridElement.BeginUpdate();
            var gridViewLookUpColumn = ((GridViewLookUpColumn)(radGridView1.CurrentRow.Cells["column1"].ColumnInfo));

            if (gridViewLookUpColumn == null) return;

            gridViewLookUpColumn.DataSource = FillData();
            gridViewLookUpColumn.DisplayMember = "Name";
            gridViewLookUpColumn.ValueMember = "Id";
            gridViewLookUpColumn.DropDownStyle = RadDropDownStyle.DropDownList;

            radGridView1.GridElement.EndUpdate();
        }

        private static DataTable FillData()
        {
            var dt = new DataTable();
            dt.Columns.Add(new DataColumn("Name", typeof(String)));
            dt.Columns.Add(new DataColumn("Id", typeof(Int32)));

            var dr = dt.NewRow();
            dr["Name"] = "Test 1";
            dr["Id"] = 1;
            dt.Rows.Add(dr);

            dr = dt.NewRow();
            dr["Name"] = "Test 2";
            dr["Id"] = "2";
            dt.Rows.Add(dr);
            return dt;
        }

 private void radGridView1_CellBeginEdit(object sender, GridViewCellCancelEventArgs e)
        {
            BindData();
        }

        private void radGridView1_CellEndEdit(object sender, GridViewCellEventArgs e)
        {
            try
            {
                var radEditor = radGridView1.ActiveEditor;

                if (radEditor == null) return;
                switch (radEditor.GetType().Name)
                {
                    case "RadComboBoxEditor":
                        {

                            var element = ((RadComboBoxElement)((RadComboBoxEditor)radGridView1.ActiveEditor).EditorElement);
                           
                            if (element == null) return;
                            var selectedText = ((RadComboBoxItem) element.SelectedItem).Text;
                            MessageBox.Show("Begin" + selectedText);

                            radGridView1.CurrentRow.Cells["column1"].CellElement.Text = selectedText;
                            //radGridView1.Rows[e.RowIndex + 1].Cells[e.ColumnIndex + 1].Value = element.SelectedValue;                                
                            break;
                        }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

Right-to-left Language and Localization Support

GridCellElement cell = e.CellElement;

cell.Controls.Add(createChart(series1Val, series2Val));