C# excel导出时根据数据库的内容自动合并单元格

/// <summary>        /// 构造函数，新建一个工作簿        /// </summary>        public ExcelHelper()        {            //创建一个Application对象并使其可见            beforeTime = DateTime.Now;            app = new Excel.ApplicationClass();            app.Visible = true;            afterTime = DateTime.Now;            //新建一个WorkBook            workBook = app.Workbooks.Add(Type.Missing);            //得到WorkSheet对象            workSheet = (Excel.Worksheet)workBook.Sheets.get_Item(1);        }        #endregion

/// <summary>        /// 将DataTable数据写入Excel文件（不分页）        /// </summary>        /// <param name="dt">DataTable</param>        /// <param name="top">表格数据起始行索引</param>        /// <param name="left">表格数据起始列索引</param>        public void DataTableToExcel(System.Data.DataTable dt, int top, int left)        {            int rowCount = dt.Rows.Count;  //DataTable行数            int colCount = dt.Columns.Count; //DataTable列数            //利用二维数组批量写入            string[,] arr = new string[rowCount, colCount];            for (int j = 0; j < rowCount; j++)            {                for (int k = 0; k < colCount; k++)                {                    arr[j, k] = dt.Rows[j][k].ToString();                }            }            range = (Excel.Range)workSheet.Cells[top, left];            range = range.get_Resize(rowCount, colCount);            range.Value2 = arr;        }