各位大侠，帮忙看看我的代码有什么问题，怎么解决？万分感谢！！！
 
protected void btnocexport_Click(object sender, EventArgs e)
    {
        StringBuilder sqlsb = new StringBuilder("SELECT ID,Date,Batch_Job,OC_Rsync,SU_Rsync FROM IT_BatchJob WHERE 1=1");

        if (this.txtdate.Text.ToString() != "" && this.txtenddate.Text.ToString() == "")
            sqlsb.Append(" AND Date = '" + this.txtdate.Text.ToString().Trim().Replace("'", "''") + "'");
        if (this.txtdate.Text.ToString() != "" && this.txtenddate.Text.ToString() != "")
            sqlsb.Append(" AND Date >= '" + this.txtdate.Text.ToString().Trim().Replace("'", "''") + "' AND Date <= '" + this.txtenddate.Text.ToString().Trim().Replace("'", "''") + "'");

        ViewState["_VsSql"] = sqlsb.ToString();
        //输出SQL语句
        //Response.Write(ViewState["_VsSql"]);
        using (DBSql db = new DBSql())
        {
            DataTable dt = db.QueryDt(ViewState["_VsSql"].ToString());




            string saveFileName = "";
            bool fileSaved = false;
            System.Windows.Forms.SaveFileDialog saveDialog = new System.Windows.Forms.SaveFileDialog();
            saveDialog.DefaultExt = "xls";
            saveDialog.Filter = "Excel文件|*.xls";
            saveDialog.FileName = "Sheet1";
            saveDialog.ShowDialog();//执行到这里出错：错误提示：在可以调用 OLE 之前，必须将当前线程设置为单线程单元(STA)模式。请确保您的 Main 函数带有 STAThreadAttribute 标记。 只有将调试器附加到该进程才会引发此异常。 

            saveFileName = saveDialog.FileName;
            if (saveFileName.IndexOf(":") < 0) return; //被点了取消 

            Microsoft.Office.Interop.Excel.Application xlApp = new Microsoft.Office.Interop.Excel.Application();

            if (xlApp == null)
            {
                System.Windows.Forms.MessageBox.Show("无法创建Excel对象，可能您的机子未安装Excel");
                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






            int rows = dt.Rows.Count; //行数
            int columns = dt.Columns.Count;//列数

            Workbook book = new Workbook();
            Worksheet sheet = new Worksheet("sheet1");
            //Excel列名
            sheet.Cells[0, 0] = new Cell("ID");
            sheet.Cells[0, 1] = new Cell("Date");
            sheet.Cells[0, 2] = new Cell("Batch Job");
            sheet.Cells[0, 3] = new Cell("OC Rsync");
            sheet.Cells[0, 4] = new Cell("SU Rsync");


            string value = "";

            for (int r = 0; r < rows; r++)
            {
                for (int c = 0; c < columns; c++)
                {
                    if (dt.Rows[r][c].ToString() != "&nbsp;")
                    {
                        //value = dt.Rows[r].Cells[c].Text;
                        value = dt.Rows[r][c].ToString();
                        if (value == "True")
                        {
                            sheet.Cells[r + 1, c] = new Cell(1);
                        }
                        else if (value == "False")
                        {
                            sheet.Cells[r + 1, c] = new Cell(0);
                        }
                        else
                        {
                            sheet.Cells[r + 1, c] = new Cell(value);
                        }
                    }
                }
            }

            //book.Worksheets.Add(sheet);
            //book.Save(@"D:\导出.xls");
            worksheet.Columns.EntireColumn.AutoFit();//列宽自适应。
            //if (cmbxType.Text != "Notification")
            //{
            //    Excel.Range rg = worksheet.get_Range(worksheet.Cells[2, 2], worksheet.Cells[ds.Tables[0].Rows.Count + 1, 2]);
            //    rg.NumberFormat = "00000000";
            //}
            if (saveFileName != "")
            {
                try
                {
                    workbook.Saved = true;
                    workbook.SaveCopyAs(saveFileName);
                    fileSaved = true;
                }
                catch (Exception ex)
                {
                    fileSaved = false;
                    System.Windows.Forms.MessageBox.Show("导出文件时出错,文件可能正被打开！\n" + ex.Message);
                }
            }
            else
            {
                fileSaved = false;
            }
            xlApp.Quit();
            GC.Collect();//强行销毁 
            if (fileSaved && System.IO.File.Exists(saveFileName)) System.Diagnostics.Process.Start(saveFileName); //打开EXCEL



        }
    }