List导出到Excel文件

例如用户列表导出

using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Admin.Web.Controllers;
using Business.OrganizationManage;
using Entity.OrganizationManage;
using Model.Param.OrganizationManage;
using Util;
using Util.Model;

namespace Admin.Web.Areas.OrganizationManage.Controllers
{
    [Area("OrganizationManage")]
    public class UserController : BaseController
    {
        private UserBLL userBLL = new UserBLL();

        [HttpPost]
        public async Task<IActionResult> ExportUserJson(UserListParam param)
        {
            TData<string> obj = new TData<string>();
            TData<List<UserEntity>> userObj = await userBLL.GetList(param);
            if (userObj.Tag == 1)
            {
                string file = new ExcelHelper<UserEntity>().ExportToExcel("用户列表.xls",
                                                                          "用户列表",
                                                                          userObj.Data,
                                                                          new string[] { "UserName", "RealName", "Gender", "Mobile", "Email" });
                obj.Data = file;
                obj.Tag = 1;
            }
            return Json(obj);
        }
    }
}

用户实体类

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Numerics;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;

namespace Entity.OrganizationManage
{
    [Table("SysUser")]
    public class UserEntity : BaseExtensionEntity
    {
        [Description("用户名")]
        public string UserName { get; set; }
        public string Password { get; set; }
        [JsonIgnore]
        public string Salt { get; set; }
        [Description("真实姓名")]
        public string RealName { get; set; }
        [Description("性别")]
        public int? Gender { get; set; }
        public string Birthday { get; set; }
        public string Portrait { get; set; }
        public string Email { get; set; }
        [Description("手机号")]
        public string Mobile { get; set; }
        public string QQ { get; set; }
        public string Wechat { get; set; }
        public int? LoginCount { get; set; }
        public int? UserStatus { get; set; }

        /// <summary>
        /// 角色Id
        /// </summary>
        [NotMapped]
        public string RoleIds { get; set; }
    }
}

ExportToExcel方法如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.IO;
using System.Linq;
using System.Reflection;
using NPOI.HSSF.UserModel;
using NPOI.XSSF.UserModel;
using NPOI.SS.UserModel;
using NPOI.SS.Util;

namespace Util
{
    /// <summary>
    /// List导出到Excel文件
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class ExcelHelper<T> where T : new()
    {
        #region List导出到Excel文件
        /// <summary>
        /// List导出到Excel文件
        /// </summary>
        /// <param name="sFileName"></param>
        /// <param name="sHeaderText"></param>
        /// <param name="list"></param>
        public string ExportToExcel(string sFileName, string sHeaderText, List<T> list, string[] columns)
        {
            sFileName = string.Format("{0}_{1}", SecurityHelper.GetGuid(), sFileName);
            string sRoot = GlobalContext.HostingEnvironment.ContentRootPath;
            string partDirectory = string.Format("Resource{0}Export{0}Excel", Path.DirectorySeparatorChar);
            string sDirectory = Path.Combine(sRoot, partDirectory);
            string sFilePath = Path.Combine(sDirectory, sFileName);
            if (!Directory.Exists(sDirectory))
            {
                Directory.CreateDirectory(sDirectory);
            }
            using (MemoryStream ms = CreateExportMemoryStream(list, sHeaderText, columns))
            {
                using (FileStream fs = new FileStream(sFilePath, FileMode.Create, FileAccess.Write))
                {
                    byte[] data = ms.ToArray();
                    fs.Write(data, 0, data.Length);
                    fs.Flush();
                }
            }
            return partDirectory + Path.DirectorySeparatorChar + sFileName;
        }

        /// <summary>  
        /// List导出到Excel的MemoryStream  
        /// </summary>  
        /// <param name="list">数据源</param>  
        /// <param name="sHeaderText">表头文本</param>  
        /// <param name="columns">需要导出的属性</param>  
        private MemoryStream CreateExportMemoryStream(List<T> list, string sHeaderText, string[] columns)
        {
            HSSFWorkbook workbook = new HSSFWorkbook();
            ISheet sheet = workbook.CreateSheet();

            Type type = typeof(T);
            PropertyInfo[] properties = ReflectionHelper.GetProperties(type, columns);

            ICellStyle dateStyle = workbook.CreateCellStyle();
            IDataFormat format = workbook.CreateDataFormat();
            dateStyle.DataFormat = format.GetFormat("yyyy-MM-dd");
            //单元格填充循环外设定单元格格式，避免4000行异常
            ICellStyle contentStyle = workbook.CreateCellStyle();
            contentStyle.Alignment = HorizontalAlignment.Left;
            contentStyle.WrapText = true;
            contentStyle.VerticalAlignment = VerticalAlignment.Center;
            #region 取得每列的列宽（最大宽度）
            int[] arrColWidth = new int[properties.Length];
            for (int columnIndex = 0; columnIndex < properties.Length; columnIndex++)
            {
                //GBK对应的code page是CP936
                arrColWidth[columnIndex] = properties[columnIndex].Name.Length;
            }
            #endregion
            for (int rowIndex = 0; rowIndex < list.Count; rowIndex++)
            {
                #region 新建表，填充表头，填充列头，样式
                if (rowIndex == 65535 || rowIndex == 0)
                {
                    if (rowIndex != 0)
                    {
                        sheet = workbook.CreateSheet();
                    }

                    #region 表头及样式
                    {
                        IRow headerRow = sheet.CreateRow(0);
                        headerRow.HeightInPoints = 25;
                        headerRow.CreateCell(0).SetCellValue(sHeaderText);

                        ICellStyle headStyle = workbook.CreateCellStyle();
                        headStyle.Alignment = HorizontalAlignment.Center;
                        IFont font = workbook.CreateFont();
                        font.FontHeightInPoints = 20;
                        font.Boldweight = 700;
                        headStyle.SetFont(font);

                        headerRow.GetCell(0).CellStyle = headStyle;

                        sheet.AddMergedRegion(new CellRangeAddress(0, 0, 0, properties.Length - 1));
                    }
                    #endregion

                    #region 列头及样式
                    {
                        IRow headerRow = sheet.CreateRow(1);
                        ICellStyle headStyle = workbook.CreateCellStyle();
                        headStyle.Alignment = HorizontalAlignment.Center;
                        IFont font = workbook.CreateFont();
                        font.FontHeightInPoints = 10;
                        font.Boldweight = 700;
                        headStyle.SetFont(font);

                        for (int columnIndex = 0; columnIndex < properties.Length; columnIndex++)
                        {
                            // 类属性如果有Description就用Description当做列名
                            DescriptionAttribute customAttribute = (DescriptionAttribute)Attribute.GetCustomAttribute(properties[columnIndex], typeof(DescriptionAttribute));
                            string description = properties[columnIndex].Name;
                            if (customAttribute != null)
                            {
                                description = customAttribute.Description;
                            }
                            headerRow.CreateCell(columnIndex).SetCellValue(description);
                            headerRow.GetCell(columnIndex).CellStyle = headStyle;
                            //根据表头设置列宽  
                            sheet.SetColumnWidth(columnIndex, (arrColWidth[columnIndex] + 1) * 256);
                        }
                    }
                    #endregion
                }
                #endregion

                #region 填充内容
                IRow dataRow = sheet.CreateRow(rowIndex + 2); // 前面2行已被占用
                for (int columnIndex = 0; columnIndex < properties.Length; columnIndex++)
                {
                    ICell newCell = dataRow.CreateCell(columnIndex);
                    newCell.CellStyle = contentStyle;
                    string drValue = properties[columnIndex].GetValue(list[rowIndex], null).ParseToString();
                    //根据单元格内容设定列宽
                    int length = (System.Text.Encoding.UTF8.GetBytes(drValue).Length + 1) * 256;
                    //超出固定宽度，按固定宽度显示（上面已设置自动换行）（注意：POI 把 列宽 > 255 视为非法值，会抛异常；）
                    if (length > 120 * 256)
                    {
                        length = 120 * 256;
                    }
                    if (sheet.GetColumnWidth(columnIndex) < length && !drValue.IsEmpty())
                    {
                        sheet.SetColumnWidth(columnIndex, length);
                    }

                    switch (properties[columnIndex].PropertyType.ToString())
                    {
                        case "System.String":
                            newCell.SetCellValue(drValue);
                            break;

                        case "System.DateTime":
                        case "System.Nullable`1[System.DateTime]":
                            newCell.SetCellValue(drValue.ParseToDateTime());
                            newCell.CellStyle = dateStyle; //格式化显示  
                            break;

                        case "System.Boolean":
                        case "System.Nullable`1[System.Boolean]":
                            newCell.SetCellValue(drValue.ParseToBool());
                            break;

                        case "System.Byte":
                        case "System.Nullable`1[System.Byte]":
                        case "System.Int16":
                        case "System.Nullable`1[System.Int16]":
                        case "System.Int32":
                        case "System.Nullable`1[System.Int32]":
                            newCell.SetCellValue(drValue.ParseToInt());
                            break;

                        case "System.Int64":
                        case "System.Nullable`1[System.Int64]":
                            newCell.SetCellValue(drValue.ParseToString());
                            break;

                        case "System.Double":
                        case "System.Nullable`1[System.Double]":
                            newCell.SetCellValue(drValue.ParseToDouble());
                            break;

                        case "System.Single":
                        case "System.Nullable`1[System.Single]":
                            newCell.SetCellValue(drValue.ParseToDouble());
                            break;

                        case "System.Decimal":
                        case "System.Nullable`1[System.Decimal]":
                            newCell.SetCellValue(drValue.ParseToDouble());
                            break;

                        case "System.DBNull":
                            newCell.SetCellValue(string.Empty);
                            break;

                        default:
                            newCell.SetCellValue(string.Empty);
                            break;
                    }
                }
                #endregion
            }

            using (MemoryStream ms = new MemoryStream())
            {
                workbook.Write(ms);
                workbook.Close();
                ms.Flush();
                ms.Position = 0;
                return ms;
            }
        }
        #endregion
    }
}