C# MVC 控制器导出Excel文件 NPOI导出Excel文件 集合转datatable NPOI设置Excel样式 NPOI设置宽高

代码如下： 
这个是将datatable转为Excel文件或文件流的方法，下面还会展示将对象集合转datatable的方法；

   /// 

        /// 将DataTable导出Excel
        /// 
        /// 
        public static string ExportDataTable(ref MemoryStream ms, DataTable dt, int type = 0, string path = "")
        {
            try
            {
                //创建Excel文件的对象
                NPOI.HSSF.UserModel.HSSFWorkbook book = new NPOI.HSSF.UserModel.HSSFWorkbook();
                //添加一个sheet
                NPOI.SS.UserModel.ISheet sheet1 = book.CreateSheet("Sheet1");
                //给sheet1添加第一行的头部标题
                NPOI.SS.UserModel.IRow row1 = sheet1.CreateRow(0);
                int i = 0;
                //自动换行给内容较多的单元格用的样式
                ICellStyle styleTitle = book.CreateCellStyle();
                styleTitle.WrapText = true;//自动换行
                styleTitle.Alignment = HorizontalAlignment.CenterSelection;
                //设置标题列
                foreach (DataColumn column in dt.Columns)
                {
                    row1.CreateCell(i).SetCellValue(column.ColumnName);
                    i++;
                }
                int j = 0;
                //把DataTable写入到Excel
                foreach (DataRow dr in dt.Rows)
                {
                    i = 0;
                    NPOI.SS.UserModel.IRow rowtemp = sheet1.CreateRow(j + 1);
                    for (; i < dt.Columns.Count; i++)
                    {
                        //判断是数字还是字符串的格式导入
                        double vsNum;
                        if(double.TryParse(dr[i].ToString(), System.Globalization.NumberStyles.Float,System.Globalization.NumberFormatInfo.InvariantInfo,out vsNum))
                            rowtemp.CreateCell(i).SetCellValue(vsNum);
                        else rowtemp.CreateCell(i).SetCellValue(dr[i].ToString());
                    }
                    rowtemp.Cells[3].CellStyle = styleTitle;
                    rowtemp.HeightInPoints = 50;
                    j++;
                }
                //最后加入函数列（我这里是做统计）
                NPOI.SS.UserModel.IRow rowtemp1 = sheet1.CreateRow(j + 1);
                for (int k = 0; k < dt.Columns.Count; k++)
                {
                    rowtemp1.CreateCell(k).SetCellValue("");
                }
                //对需要统计的列添加函数
                rowtemp1.Cells[5].SetCellValue("总 计");
                rowtemp1.Cells[6].SetCellFormula("sum(G2:G"+(dt.Rows.Count+1)+")");
                rowtemp1.Cells[8].SetCellFormula("sum(I2:I" + (dt.Rows.Count + 1) + ")");
                rowtemp1.Cells[10].SetCellFormula("sum(K2:K" + (dt.Rows.Count + 1) + ")");
                rowtemp1.Cells[11].SetCellFormula("sum(L2:L" + (dt.Rows.Count + 1) + ")");
                rowtemp1.Cells[14].SetCellFormula("sum(O2:O" + (dt.Rows.Count + 1) + ")");
                if (type == 0)
                {
                    //设置列宽
                    sheet1.SetColumnWidth(3,40 * 256);
                    sheet1.AutoSizeColumn(4);
                    sheet1.AutoSizeColumn(0);
                    sheet1.DefaultColumnWidth =8;
                    MemoryStream ms1 = new MemoryStream();
                    book.Write(ms1);
                    ms1.Seek(0, SeekOrigin.Begin);
                    ms = ms1;
                }
                else
                {
                    FileStream fs = new FileStream(path, FileMode.Create);
                    book.Write(fs);
                    fs.Close();
                    ms = null;
                }
                return "成功";
            }
            catch (Exception ex)
            {
                ms = null;
                return  ex.ToString();
            }
        }

下面是将对象集合转为datatable的方法：
 

 /// 
    
        /// 将集合类转换成DataTable    
        /// 
    
        /// 集合    
        ///     
        public static DataTable ToDataTable(IList list)
        {
            DataTable result = new DataTable();
            if (list.Count > 0)
            {
                PropertyInfo[] propertys = list[0].GetType().GetProperties();

                foreach (PropertyInfo pi in propertys)
                {
                    result.Columns.Add(pi.Name, pi.PropertyType);
                }
                foreach (object t in list)
                {
                    ArrayList tempList = new ArrayList();
                    foreach (PropertyInfo pi in propertys)
                    {
                        object obj = pi.GetValue(t, null);
                        tempList.Add(obj);
                    }
                    object[] array = tempList.ToArray();
                    result.LoadDataRow(array, true);
                }
            }
            return result;
        }