if (cell.IsMergedCell)

                        for (int ii = 0; ii < sheet.NumMergedRegions; ii++)
                        {
                            var cellrange = sheet.GetMergedRegion(ii);
                            if (cell.ColumnIndex >= cellrange.FirstColumn && cell.ColumnIndex <= cellrange.LastColumn
                                && cell.RowIndex >= cellrange.FirstRow && cell.RowIndex <= cellrange.LastRow)
                            {
                                // 这里是cell所在的合并单元格，添加处理代码
                            }
                        }