1、新增程式包。

在專案名右鍵。

選擇管理NuGet程式包，瀏覽處搜尋NPOI並安裝。

2、程式碼引用。

using System.IO;
using System.Data.SqlClient;
using System.Diagnostics;
using NPOI.HSSF.UserModel;
using NPOI.SS.UserModel;
using NPOI.XSSF.UserModel;

3、匯出Excel方法：

public void ExportDataToExcel(DataTable TableName, string FileName)
        {
            SaveFileDialog saveFileDialog 
 
= new SaveFileDialog();
            //設定檔案標題
            saveFileDialog.Title = "匯出Excel檔案";
            //設定檔案型別
            saveFileDialog.Filter = "Excel 工作簿(*.xlsx)|*.xlsx|Excel 97-2003 工作簿(*.xls)|*.xls";
            //設定預設檔案型別顯示順序  
            saveFileDialog.FilterIndex = 1;
            //是否自動在檔名中新增副檔名
            saveFileDialog.AddExtension = true
 
;
            //是否記憶上次開啟的目錄
            saveFileDialog.RestoreDirectory = true;
            //設定預設檔名
            saveFileDialog.FileName = FileName;
            //按下確定選擇的按鈕  
            if (saveFileDialog.ShowDialog() == DialogResult.OK)
            {
                //獲得檔案路徑 
                string localFilePath = saveFileDialog.FileName.ToString();

                
 
//資料初始化
                int TotalCount;     //總行數
                int RowRead = 0;    //已讀行數
                int Percent = 0;    //百分比

                TotalCount = TableName.Rows.Count;
                lblStatus.Text = "共有" + TotalCount + "條資料";
                lblStatus.Visible = true;
                barStatus.Visible = true;

                //NPOI
                IWorkbook workbook;
                string FileExt = Path.GetExtension(localFilePath).ToLower();
                if (FileExt == ".xlsx")
                {
                    workbook = new XSSFWorkbook();
                }
                else if (FileExt == ".xls")
                {
                    workbook = new HSSFWorkbook();
                }
                else
                {
                    workbook = null;
                }
                if (workbook == null)
                {
                    return;
                }
                ISheet sheet = string.IsNullOrEmpty(FileName) ? workbook.CreateSheet("Sheet1") : workbook.CreateSheet(FileName);


                //秒鐘
                Stopwatch timer = new Stopwatch();
                timer.Start();

                try
                {
                    //讀取標題  
                    IRow rowHeader = sheet.CreateRow(0);
                    for (int i = 0; i < TableName.Columns.Count; i++)
                    {
                        ICell cell = rowHeader.CreateCell(i);
                        cell.SetCellValue(TableName.Columns[i].ColumnName);
                    }

                    //讀取資料  
                    for (int i = 0; i < TableName.Rows.Count; i++)
                    {
                        IRow rowData = sheet.CreateRow(i + 1);
                        for (int j = 0; j < TableName.Columns.Count; j++)
                        {
                            ICell cell = rowData.CreateCell(j);
                            cell.SetCellValue(TableName.Rows[i][j].ToString());
                        }
                        //狀態列顯示
                        RowRead++;
                        Percent = (int)(100 * RowRead / TotalCount);
                        barStatus.Maximum = TotalCount;
                        barStatus.Value = RowRead;
                        lblStatus.Text = "共有" + TotalCount + "條資料，已讀取" + Percent.ToString() + "%的資料。";
                        Application.DoEvents();
                    }

                    //狀態列更改
                    lblStatus.Text = "正在生成Excel...";
                    Application.DoEvents();

                    //轉為位元組陣列  
                    MemoryStream stream = new MemoryStream();
                    workbook.Write(stream);
                    var buf = stream.ToArray();

                    //儲存為Excel檔案  
                    using (FileStream fs = new FileStream(localFilePath, FileMode.Create, FileAccess.Write))
                    {
                        fs.Write(buf, 0, buf.Length);
                        fs.Flush();
                        fs.Close();
                    }

                    //狀態列更改
                    lblStatus.Text = "生成Excel成功，共耗時" + timer.ElapsedMilliseconds + "毫秒。";
                    Application.DoEvents();
                    
                    //關閉秒鐘
                    timer.Reset();
                    timer.Stop();

                    //成功提示
                    if (MessageBox.Show("匯出成功，是否立即開啟？", "提示", MessageBoxButtons.YesNo, MessageBoxIcon.Information) == DialogResult.Yes)
                    {
                        System.Diagnostics.Process.Start(localFilePath);
                    }

                    //賦初始值
                    lblStatus.Visible = false;
                    barStatus.Visible = false;
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message, "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }
                finally
                {
                    //關閉秒鐘
                    timer.Reset();
                    timer.Stop();
                    //賦初始值
                    lblStatus.Visible = false;
                    barStatus.Visible = false;
                }
            }
        }

4、結果演示：

轉 ：https://www.cnblogs.com/zxh1314/p/8342066.html

https://www.cnblogs.com/lazyneal/p/6148912.html