using System.IO;
using System.Data;
using System;
using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;

namespace 优软MES.DataOperate
{
    class ExcelHandler
    {
        DataHelper dh = new DataHelper();
        /// <summary>
        /// 导出Excel
        /// </summary
        public  void ExportExcel(DataTable dt,string FolderPath) {
            //创建一个内存流，用来接收转换成Excel的内容
            MemoryStream ms;
            ms = DataTableToExcel(dt);
            //以系统当前时间命名文件，FileMode.Create表示创建文件，FileAccess.Write表示拥有写的权限
            FileStream fs = new FileStream(@FolderPath+"\\"+DateTime.Now.ToString("yyyyMMddHHmmss") +".xls", FileMode.Create, FileAccess.Write);
            byte[] data = ms.ToArray();
            fs.Write(data, 0, data.Length);
            fs.Flush();
            //释放当前Excel文件，否则打开文件的时候会显示文件被占用
            ms.Dispose();
            fs.Dispose();
        }

        /// <summary>
        /// 导入Excel
        /// </summary>
        public void ImportExcel(DataTable DataTable, string TableName) {
            
        }
        /// <summary>
        /// 将DataTable形式的数据转成Excel格式的，然后用字节流的形式写入文件
        /// </summary>
        /// <param name="DataTable"></param>
        /// <returns></returns>
        public MemoryStream  DataTableToExcel(DataTable DataTable) {
           
            //创建内存流
            MemoryStream ms=new MemoryStream();
            //创建一个Book，相当于一个Excel文件
            HSSFWorkbook book = new HSSFWorkbook();
            //Excel中的Sheet
            ISheet sheet = book.CreateSheet("sheet1");
            //获取行数量和列数量
            int rowNum = DataTable.Rows.Count;
            int columnNum = DataTable.Columns.Count;
            //设置列的宽度，根据首行的列的内容的长度来设置
            for (int i=0;i<columnNum;i++) {
                int dataLength = DataTable.Rows[0][i].ToString().Length;
                if (dataLength <= 3)
                {
                    sheet.SetColumnWidth(i, dataLength * 1200);
                }
                else {
                    sheet.SetColumnWidth(i, dataLength * 400);
                }
            }
            //将DataTable的值循环赋值给book，Aligment设置居中
            for (int i = 0; i < rowNum; i++) {
                IRow row = sheet.CreateRow(i);
                row.HeightInPoints = 20;
                for (int j = 0; j < columnNum; j++) {
                    row.CreateCell(j).SetCellValue(DataTable.Rows[i][j].ToString());
                    row.GetCell(j).CellStyle.Alignment = HorizontalAlignment.CENTER;
                }
            }
            //将book的内容写入内存流中返回
            book.Write(ms);
            return ms;
        }
    }
}