1.首先在當前專案中新增引用NPOI.dll

2.在專案中新增類ExportExcel.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Collections;
using System.Data;
using System.Windows.Forms;
using NPOI;
using NPOI.Util;
using NPOI.HPSF;
using NPOI.HSSF.UserModel;
using NPOI.HSSF.Util;
using NPOI.POIFS;
using NPOI.POIFS.FileSystem;
using NPOI.SS.Util;
using NPOI.SS.UserModel;


namespace 測試
{
    public class ExportExcel
    {
        static IWorkbook hssfworkbook;
        #region 匯出Excel
        /// <summary>
        /// 使用DataTable匯出資料
        /// </summary>
        /// <param name="dt">資料</param>
        /// <param name="FileName">檔名</param>
        /// <param name="msg">提示訊息</param>
        public static void DtToExcel(DataTable dt, string FileName)
        {
            try
            {
                if (dt != null && dt.Rows.Count > 0)
                {
                    SaveFileDialog dlg = new SaveFileDialog();//申明儲存對話方塊
                    dlg.Filter = "Excel檔案|*.xls";
                    dlg.FileName = FileName;//預設檔名稱
                    if (dlg.ShowDialog() == DialogResult.Cancel)
                        return;
                    dlg.InitialDirectory = Directory.GetCurrentDirectory();//返回檔案路徑
                    string filename = dlg.FileName;//輸出的檔名稱
                    if (filename.Trim() == " ")//驗證strFileName是否為空或值無效
                    { return; }
                    hssfworkbook = new HSSFWorkbook();
                    ISheet sheet = hssfworkbook.CreateSheet("Sheet1");

                    int colscount = dt.Columns.Count;//定義表格內資料的列數               
                    ArrayList arr = new ArrayList();//儲存頭資訊
                    ICellStyle cstyle = hssfworkbook.CreateCellStyle();

                    IRow rowHeader = sheet.CreateRow(0);//建立列頭資料
                    int displayColumnsCount = 0;//用於處理隱藏列頭不被顯示         

                    HSSFFont hssffont = hssfworkbook.CreateFont() as HSSFFont;
                    hssffont.FontHeightInPoints = 11;

                    //設定單元格邊框 
                    for (int i = 0; i < dt.Columns.Count; i++)//生成表頭資訊
                    {
                        ICell cell = rowHeader.CreateCell(displayColumnsCount);
                        cell.SetCellValue(dt.Columns[i].ToString());
                        sheet.SetColumnWidth(displayColumnsCount, 17 * 256);
                        displayColumnsCount++;
                        arr.Add(dt.Columns[i].ToString());
                    }
                    for (int i = 0; i < dt.Rows.Count; i++)
                    {
                        IRow irow = sheet.CreateRow(i + 1);
                        for (int j = 0; j < dt.Columns.Count - 1; j++)
                        {
                            ICell cell = irow.CreateCell(j);
                            cell.SetCellValue(dt.Rows[i][j].ToString());
                        }
                    }
                    using (Stream stream = File.OpenWrite(filename))
                    {
                        hssfworkbook.Write(stream);
                        MessageBox.Show(filename + "\n\n匯出完畢! ", "提示 ", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    }
                }
                else
                {
                    MessageBox.Show("沒有資料可供匯出", "提示");
                }
            }
            catch
            {
                MessageBox.Show("操作失敗", "提示");
            }
        }
        #endregion

    }
}
 

private void btExport_Click(object sender, EventArgs e)
        {
            if (this.dgvdata.Rows.Count == 0)
            {
                MessageBox.Show("未能查詢到資料！！！","提示");
                return;
            }

            ExportExcel.DtToExcel(dt, "預設檔名");
        }
 

4.除錯程式，點選button按鈕，可以匯出資料

NPOI下載地址：