关于vs2008 C#导出Excel2007的问题
winform中读取了数据库的数据，保存在数据集ds中，想把这些数据导出为一个Excel表格，但是导出时出现问题，代码如下：
            
            SaveFileDialog sfd = new SaveFileDialog();
            sfd.Filter = "excel files (*.xls)|*.xls|All files (*.*)|*.*";
            sfd.FilterIndex = 1;
            sfd.RestoreDirectory = true;
            if (sfd.ShowDialog() == DialogResult.OK)
            {
                Excel.ApplicationClass xlApp = new Excel.ApplicationClass();
                if (xlApp == null)
                {
                    MessageBox.Show("无法创建Excel文档");
                }
                else
                {
                    //Excel.Workbook workbook = xlApp.Workbooks.Add(true);
                    Excel.Workbook workbook = xlApp.Workbooks.Add(Excel.XlWBATemplate.xlWBATWorksheet);
                    Excel.Worksheet worksheet = (Excel.Worksheet)workbook.Worksheets[1];
                    for (int i = 0; i < ds.Tables[0].Columns.Count; i++)
                    {
                        //先只保存一个表头
                        worksheet.Cells[1, i] = ds.Tables[0].Columns[i].ColumnName;
                    }
                
                    workbook.Saved = true;
                    workbook.SaveCopyAs(sfd.FileName);
                }
               
         &n