private void button5_Click(object sender, EventArgs e)
 {
    datatable dt=new datatable();   //需要轉換的資料表

    ExportToExcel(dt,"excel表格名");
}


///datatable匯出Excel表格函式
public void ExportToExcel(DataTable dt, string saveFileName)
        {
            if (dt == null) return;
            Microsoft.Office.Interop.Excel.Application xlApp = new Microsoft.Office.Interop.Excel.Application();
            if (xlApp == null)
            {
                // lblMsg.Text = "無法建立Excel物件，可能您的機子未安裝Excel";
                MessageBox.Show("請確保您的電腦已經安裝Excel", "提示資訊", MessageBoxButtons.OK, MessageBoxIcon.Error);
                return;
            }
            Microsoft.Office.Interop.Excel.Workbooks workbooks = xlApp.Workbooks;
            Microsoft.Office.Interop.Excel.Workbook workbook = workbooks.Add(Microsoft.Office.Interop.Excel.XlWBATemplate.xlWBATWorksheet);
            Microsoft.Office.Interop.Excel.Worksheet worksheet = (Microsoft.Office.Interop.Excel.Worksheet)workbook.Worksheets[1]; //取得sheet1
            Microsoft.Office.Interop.Excel.Range range = null;
            long totalCount = dt.Rows.Count;
            long rowRead = 0;
            float percent = 0;

            //寫入標題
            for (int i = 0; i < dt.Columns.Count; i++)
            {
                worksheet.Cells[1, i + 1] = dt.Columns[i].ColumnName;
                range = (Microsoft.Office.Interop.Excel.Range)worksheet.Cells[1, i + 1];
                range.Interior.ColorIndex = 15;//背景顏色
                range.Font.Bold = true; //粗體
                range.HorizontalAlignment = Microsoft.Office.Interop.Excel.XlHAlign.xlHAlignCenter; //居中
                //加邊框
                range.BorderAround(Microsoft.Office.Interop.Excel.XlLineStyle.xlContinuous, Microsoft.Office.Interop.Excel.XlBorderWeight.xlThin,
                                  Microsoft.Office.Interop.Excel.XlColorIndex.xlColorIndexAutomatic, null);
                //range.ColumnWidth = 4.63;//設定列寬
                //range.EntireColumn.AutoFit();//自動調整列寬
                //r1.EntireRow.AutoFit();//自動調整行高
            }
            //寫入內容
            for (int r = 0; r < dt.Rows.Count; r++)
            {
                for (int i = 0; i < dt.Columns.Count; i++)
                {
                    try
                    {
                        worksheet.Cells[r + 2, i + 1] = dt.Rows[r][i];

                        range = (Microsoft.Office.Interop.Excel.Range)worksheet.Cells[r + 2, i + 1];
                        range.Font.Size = 9; //字型大小
                        //加邊框
                        range.BorderAround(Microsoft.Office.Interop.Excel.XlLineStyle.xlContinuous, Microsoft.Office.Interop.Excel.XlBorderWeight.xlThin,
                                          Microsoft.Office.Interop.Excel.XlColorIndex.xlColorIndexAutomatic, null);
                        range.EntireColumn.AutoFit(); //自動調整列寬
                    }
                    catch (Exception)
                    {
                    }
                }
                rowRead++;
                percent = ((float)(100 * rowRead)) / totalCount;
                Application.DoEvents();
            }

            range.Borders[Microsoft.Office.Interop.Excel.XlBordersIndex.xlInsideHorizontal].Weight = Microsoft.Office.Interop.Excel.XlBorderWeight.xlThin;
            if (dt.Columns.Count > 1)
            {
                range.Borders[Microsoft.Office.Interop.Excel.XlBordersIndex.xlInsideVertical].Weight = Microsoft.Office.Interop.Excel.XlBorderWeight.xlThin;
            }

            try
            {
                workbook.Saved = true;

                SaveFileDialog SaveFile = new SaveFileDialog();
                SaveFile.FileName = saveFileName;
                //SaveFile.Filter = "Miscrosoft Office Excel 97-2003 工作表|*.xls|所有檔案(*.*)|*.*";
                SaveFile.Filter = "Miscrosoft Office Excel 97-2003 工作表|*.xls|Excel 工作簿|*.xlsx|所有檔案(*.*)|*.*";
                SaveFile.RestoreDirectory = true;
                if (SaveFile.ShowDialog() == DialogResult.OK)
                {
                    workbook.SaveCopyAs(SaveFile.FileName);

                    MessageBox.Show("匯出資料成功!", "系統資訊", MessageBoxButtons.OK, MessageBoxIcon.Information);
                }
            }
            catch (Exception ex)
            {
                //MessageBox.Show("匯出檔案時出錯,檔案可能正被開啟!", "系統資訊");
                MessageBox.Show(ex.Message.ToString());
            }

            //在關閉時會卡死程式，暫未測試原因
            //try
            //{

            //    workbooks.Close();
            //    if (xlApp != null)
            //    {
            //        xlApp.Workbooks.Close();

            //        xlApp.Quit();

            //        int generation = GC.GetGeneration(xlApp);
            //        System.Runtime.InteropServices.Marshal.ReleaseComObject(xlApp);

            //        xlApp = null;
            //        GC.Collect(generation);
            //    }
            //    GC.Collect(); //強行銷燬
            //}
            //catch (Exception ex) {
            //    MessageBox.Show("coles error!!!");
            //}

            //#region 強行殺死最近開啟的Excel程序

            //System.Diagnostics.Process[] excelProc = System.Diagnostics.Process.GetProcessesByName("EXCEL");
            //DateTime startTime = new DateTime();
            //int m = 0;
            //int killId = 0;
            //for (m = 0; m < excelProc.Length; m++)
            //{
            //    if (startTime < excelProc[m].StartTime)
            //    {
            //        startTime = excelProc[m].StartTime;
            //        killId = m;
            //    }
            //}
            //try
            //{
            //    if (killId > 0 && excelProc[killId].HasExited == false)
            //    {
            //        excelProc[killId].Kill();
            //    }
            //}
            //catch (Exception ex)
            //{

            //}
            //#endregion
        }