写入数据到Excel

---------------------DownloadExcelAsStreame<T>(IList<T> param, string sheetname=null) where T : new()------------------

依赖：

　　|-NPOI

　　|-Newtonsoft

备注：

这里为了方便，么有自己定义Attribute，用Josn的Attribute来给类型带入参数。

注意：

这个版本的NPOI写入Excel，单个文件最多只能写入65536行，如果不满足需要可以转写入CVS（CVS不限制大小）

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 public static MemoryStream DownloadExcelAsStreame<T>(IList<T> param, string sheetname=null) where T : new()
 {
      if (param == null || param.Count < 1)
                return null;
            int rowsCount = param.Count(),columnCount = param.FirstOrDefault().GetType().GetProperties().Count(p => p.PropertyType.IsPublic);
            var tp= typeof (T);
            var tpattr = tp.GetCustomAttribute<JsonObjectAttribute>();
            if (tpattr == null)
                return null;
            HSSFWorkbook workbook = new HSSFWorkbook();
            HSSFSheet sheet = workbook.CreateSheet(sheetname?? tpattr.Id) as HSSFSheet;
            HSSFRow headerRow = sheet.CreateRow(0) as HSSFRow;
            List<PropertyInfo> pts = tp.GetProperties().Where(p => p.PropertyType.IsPublic).Select(o => o).ToList();
            string[] atv = pts.ConvertAll(ii =>
            {
                var jsonPropertyAttribute = ii.GetCustomAttribute<JsonPropertyAttribute>();
                if (jsonPropertyAttribute != null)
                    return jsonPropertyAttribute.PropertyName;
                return string.Empty;
            }).ToArray();
            var me = new MemoryStream();
            int paddingrow = 0;
            int rowindex = 0;
            for (int nn = 0; nn < columnCount; nn++)
            {
                if (!string.IsNullOrEmpty(atv[nn]))
                {
                    headerRow.CreateCell(rowindex, NPOI.SS.UserModel.CellType.String).SetCellValue(atv[nn] ?? pts[nn].Name);
                    rowindex++;
                }
            }
            paddingrow += 1;
            rowindex = 0;
            for (int r = 0; r < rowsCount; r++)
            {
                HSSFRow cntRow = sheet.CreateRow(r + paddingrow) as HSSFRow;
                for (int pj = 0; pj < columnCount; pj++)
                {
                    if (!string.IsNullOrEmpty(atv[pj]))
                    {
                        cntRow.CreateCell(rowindex, NPOI.SS.UserModel.CellType.String)
                            .SetCellValue(pts[pj].GetValue(param[r]) != null
                                ? pts[pj].GetValue(param[r]).ToString()
                                : "");
                        rowindex++;
                    }
                }
                rowindex =0;
            }
            workbook.Write(me);
            workbook.Close();
            return me;
        }