1.

2.建立NPOIHelper

using System;
using System.Collections.Generic;
using System.Data;
using System.IO;
using System.Text;
using System.Web;
using NPOI;
using NPOI.HPSF;
using NPOI.HSSF;
using NPOI.HSSF.UserModel;
using NPOI.HSSF.Util;
using NPOI.POIFS;
using NPOI.Util;
using NPOI.SS.UserModel;
using NPOI.SS.Util;
using NPOI.XSSF.UserModel;

namespace HD.Helper.Common
{
/// <summary>
/// NPOI操作幫助類
/// </summary>
public class NPOIHelper
{
/// <summary>
/// DataTable匯出到Excel檔案
/// </summary>
/// <param name="dtSource">源DataTable</param>
/// <param name="strHeaderText">表頭文字</param>
/// <param name="strFileName">儲存位置</param>
public static void Export(DataTable dtSource, string strHeaderText, string strFileName)
{
using (MemoryStream ms = Export(dtSource, strHeaderText))
{
using (FileStream fs = new FileStream(strFileName, FileMode.Create, FileAccess.Write))
{
byte[] data = ms.ToArray();
fs.Write(data, 0, data.Length);
fs.Flush();
}
}
}

/// <summary>
/// DataTable匯出到Excel的MemoryStream
/// </summary>
/// <param name="dtSource">源DataTable</param>
/// <param name="strHeaderText">表頭文字</param>
public static MemoryStream Export(DataTable dtSource, string strHeaderText)
{
XSSFWorkbook workbook = new XSSFWorkbook();

ISheet sheet = workbook.CreateSheet();

ICellStyle dateStyle = workbook.CreateCellStyle();
IDataFormat format = workbook.CreateDataFormat();
dateStyle.DataFormat = format.GetFormat("yyyy-MM-dd");

#region 取得每列的列寬（最大寬度）
int[] arrColWidth = new int[dtSource.Columns.Count];
foreach (DataColumn item in dtSource.Columns)
{
//GBK對應的code page是CP936
arrColWidth[item.Ordinal] = Encoding.GetEncoding(936).GetBytes(item.ColumnName.ToString()).Length;
}
for (int i = 0; i < dtSource.Rows.Count; i++)
{
for (int j = 0; j < dtSource.Columns.Count; j++)
{
int intTemp = Encoding.GetEncoding(936).GetBytes(dtSource.Rows[i][j].ToString()).Length;
if (intTemp > arrColWidth[j])
{
arrColWidth[j] = intTemp;
}
}
}
#endregion

int rowIndex = 0;

foreach (DataRow row in dtSource.Rows)
{
#region 新建表，填充表頭，填充列頭，樣式
if (rowIndex == 65535 || rowIndex == 0)
{
if (rowIndex != 0)
{
sheet = workbook.CreateSheet();
}

#region 表頭及樣式
{
IRow headerRow = sheet.CreateRow(0);
headerRow.HeightInPoints = 35;
headerRow.CreateCell(0).SetCellValue(strHeaderText);

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, dtSource.Columns.Count - 1));
}
#endregion

#region 列頭及樣式
{
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);

foreach (DataColumn column in dtSource.Columns)
{
headerRow.CreateCell(column.Ordinal).SetCellValue(column.ColumnName);
headerRow.GetCell(column.Ordinal).CellStyle = headStyle;

//設定列寬
sheet.SetColumnWidth(column.Ordinal, (arrColWidth[column.Ordinal] + 1) * 256);

}
}
#endregion

rowIndex = 2;
}
#endregion

#region 填充內容
ICellStyle contentStyle = workbook.CreateCellStyle();
contentStyle.Alignment = HorizontalAlignment.Left;
IRow dataRow = sheet.CreateRow(rowIndex);
foreach (DataColumn column in dtSource.Columns)
{
ICell newCell = dataRow.CreateCell(column.Ordinal);
newCell.CellStyle = contentStyle;

string drValue = row[column].ToString();

switch (column.DataType.ToString())
{
case "System.String"://字串型別
newCell.SetCellValue(drValue);
break;
case "System.DateTime"://日期型別
DateTime dateV;
DateTime.TryParse(drValue, out dateV);
newCell.SetCellValue(dateV);

newCell.CellStyle = dateStyle;//格式化顯示
break;
case "System.Boolean"://布林型
bool boolV = false;
bool.TryParse(drValue, out boolV);
newCell.SetCellValue(boolV);
break;
case "System.Int16"://整型
case "System.Int32":
case "System.Int64":
case "System.Byte":
int intV = 0;
int.TryParse(drValue, out intV);
newCell.SetCellValue(intV);
break;
case "System.Decimal"://浮點型
case "System.Double":
double doubV = 0;
double.TryParse(drValue, out doubV);
newCell.SetCellValue(doubV);
break;
case "System.DBNull"://空值處理
newCell.SetCellValue("");
break;
default:
newCell.SetCellValue("");
break;
}

}
#endregion

rowIndex++;
}

MemoryStream ms = new MemoryStream();

workbook.Write(ms);
//sheet.Dispose();
//workbook.Dispose();//一般只用寫這一個就OK了，他會遍歷並釋放所有資源，但當前版本有問題所以只釋放sheet
return ms;

}

/// <summary>讀取excel
/// 預設第一行為標頭
/// </summary>
/// <param name="strFileName">excel文件路徑</param>
/// <returns></returns>
public static DataTable Import(string strFileName)
{
DataTable dt = new DataTable();

HSSFWorkbook hssfworkbook;
using (FileStream file = new FileStream(strFileName, FileMode.Open, FileAccess.Read))
{
hssfworkbook = new HSSFWorkbook(file);
}
ISheet sheet = hssfworkbook.GetSheetAt(0);
System.Collections.IEnumerator rows = sheet.GetRowEnumerator();

IRow headerRow = sheet.GetRow(0);
int cellCount = headerRow.LastCellNum;

for (int j = 0; j < cellCount; j++)
{
ICell cell = headerRow.GetCell(j);
dt.Columns.Add(cell.ToString());
}

for (int i = (sheet.FirstRowNum + 1); i <= sheet.LastRowNum; i++)
{
IRow row = sheet.GetRow(i);
DataRow dataRow = dt.NewRow();

for (int j = row.FirstCellNum; j < cellCount; j++)
{
if (row.GetCell(j) != null)
dataRow[j] = row.GetCell(j).ToString();
}

dt.Rows.Add(dataRow);
}
return dt;
}

}
}

3.建立控制器

public class ExportController : ApiController
{
[Route("api/Export")]
[HttpGet]
public void Export()
{
HttpContext context = HttpContext.Current;
string where = HttpUtility.HtmlDecode(context.Request["where"].ToString());
if (String.IsNullOrEmpty(where))
{
where = "1=1";
}
string filename = "標題";
SqlHelper db = new SqlHelper();
string sql = @"select id ,欄位 from table  where " + where;

DataTable dt = db.ExcuteTable(sql);
try
{
MemoryStream ms = NPOIHelper.Export(dt, filename);
context.Response.Clear();
context.Response.ContentEncoding = Encoding.GetEncoding("GB2312");
context.Response.ContentType = "application/octet-stream";
context.Response.AddHeader("Content-Disposition", "attachment;fileName=" + HttpUtility.UrlEncode(filename, Encoding.UTF8) + ".xlsx");
context.Response.BinaryWrite(ms.ToArray());
context.Response.Flush();
context.Response.End();
}
catch (Exception ex)
{

// throw ex;
}
}
}

4.前端新增標籤

<iframe id="IframeExport" src="" style="display:none;opacity:0;height:0;width:0;overflow:hidden;"></iframe>

5.傳送請求

function NpoiExcel() {

document.getElementById("IframeExport").src = "/api/Export?where=" + where.join(' AND ');
}
window.NpoiExcel = NpoiExcel;

注意：請求時的引數如果有特殊符號 比如拼接的查詢條件 帶有like '%329309239%' 需要 encodeURI()轉一下 後臺接收後 在轉一下 ，也可以將條件傳到後臺處理。