C# 在MVC 中把DataTable中的数据导出到Excel

// 类库
// NPOI.dll
// NPOI.OOXML.dll
// NPOI.OpenXml4Net.dll
// NPOI.OpenXmlFormats.dll

using NPOI.XSSF.UserModel;
using NPOI.SS.UserModel;



public class ExcelHelper
    {
        public static Stream ExportData(System.Data.DataTable dt)
        {
            if (dt == null)
            {
                throw new ArgumentNullException();
            }
            if (dt.Rows.Count > 5000)
                dt=dt.Select().Take(5000).CopyToDataTable();

            XSSFWorkbook book = new XSSFWorkbook();
            
            ISheet sheet = book.CreateSheet("sheet1");
            int rowCount = dt.Rows.Count;
            int cellCount = dt.Columns.Count;

            var titleRow = sheet.CreateRow(0);
            #region header style
            titleRow.HeightInPoints = 18;
            ICellStyle headStyle = book.CreateCellStyle();
            headStyle.Alignment = HorizontalAlignment.Center;
            IFont font = book.CreateFont();
            font.FontHeightInPoints = 12;
            font.Boldweight = 1200;
            font.Color = NPOI.HSSF.Util.HSSFColor.Green.Index;
            headStyle.SetFont(font);

            headStyle.BorderBottom = NPOI.SS.UserModel.BorderStyle.Thin;
            headStyle.BorderLeft = NPOI.SS.UserModel.BorderStyle.Thin;
            headStyle.BorderRight = NPOI.SS.UserModel.BorderStyle.Thin;
            headStyle.BorderTop = NPOI.SS.UserModel.BorderStyle.Thin;

            #endregion

            for (int i = 0; i < dt.Columns.Count; i++)
            {
                ICell cell = titleRow.CreateCell(i);
                cell.SetCellValue(dt.Columns[i].ColumnName);
                cell.CellStyle = headStyle;
            }

            for (int i = 0; i < dt.Rows.Count; i++)
            {
                IRow row = sheet.CreateRow(i + 1);
                for (int j = 0; j < cellCount; j++)
                {
                    string formattedString;
                    if (dt.Columns[j].DataType.Name == "String")
                    {
                        Encoding ascii = Encoding.ASCII;
                        Encoding unicode = Encoding.Unicode;
                        // Convert the string into a byte array.
                        byte[] unicodeBytes = unicode.GetBytes(dt.Rows[i][j].ToString());
                        // Perform the conversion from one encoding to the other.
                        byte[] asciiBytes = Encoding.Convert(unicode, ascii, unicodeBytes);
                        // Convert the new byte[] into a char[] and then into a string.
                        char[] asciiChars = new char[ascii.GetCharCount(asciiBytes, 0, asciiBytes.Length)];
                        ascii.GetChars(asciiBytes, 0, asciiBytes.Length, asciiChars, 0);
                        string asciiString = new string(asciiChars);

                        formattedString = asciiString.Replace(Convert.ToChar(0x0).ToString(), "");                       
                    }
                    else
                    {
                        formattedString = dt.Rows[i][j].ToString();
                    }

                    row.CreateCell(j).SetCellValue(formattedString);
                }
            }


            NpoiMemoryStream stream = new NpoiMemoryStream();
            stream.AllowClose = false;
            book.Write(stream);
 
            stream.Seek(0, SeekOrigin.Begin);
            stream.AllowClose = true;
            book.Close();

            return stream;
        }

        public static List<string> ImportData(Stream stream)
        {
            List<string> data = new List<string>();
            XSSFWorkbook workbook = new XSSFWorkbook(stream);
            ISheet sheet = workbook.GetSheet("Sheet1");
            for (int row = 0; row <= sheet.LastRowNum; row++)
            {
                if (sheet.GetRow(row) != null) //null is when the row only contains empty cells 
                {
                    data.Add(sheet.GetRow(row).GetCell(0).StringCellValue);
                }
            }
            return data;
        }
    }
    public class NpoiMemoryStream : MemoryStream
    {
        public NpoiMemoryStream()
        {
            AllowClose = true;
        }

        public bool AllowClose { get; set; }
        public override void Close()
        {
            if (AllowClose)
                base.Close();
        }
    }

// actionresult 调用
//
using System.Web.Mvc;
 public class QueryController : Controller{
 5  public ActionResult Excel(string region)
 {
        System.IO.Stream stream = null;

        var dt = new System.Data.DataTable();
        stream = ExcelHelper.ExportData(dt);

        return new FileStreamResult(stream, "application/ms-excel") { FileDownloadName = "Result.xlsx" };

14  }
  }

//前台调用代码
  function Download() {
            var Region = $('#Region').children("option:selected").val();
            window.location.href = '@Url.Content("~/Query/Excel?region=")'+Region; 
}

 <div class="form-inline">
                    <input type="button" value="Download" class="myButton create-btn" style="160px;" onclick="Download()" />
                </div>