/// <summary>
        ///  需要添加引用com中的"microsoft excel 11.0 object library"
        /// </summary>
        ///
        /// <param name="mydgv"></param>
        public void Exportdatagridviewtoexcel(DataGridView mydgv)
        {
            if (mydgv.Rows.Count == 0)
            {
                MessageBox.Show(" 没有数据可供导出！", "提示信息", MessageBoxButtons.OK, MessageBoxIcon.Information);
                return;
            }
            else
            {
                SaveFileDialog savedialog = new SaveFileDialog();
                savedialog.DefaultExt = "xlsx";
                savedialog.Filter = "microsoft office execl files (*.xlsx)|*.xlsx";
                savedialog.FilterIndex = 0;
                savedialog.RestoreDirectory = true;
                savedialog.Title = "导出数据到excel表格";
                savedialog.ShowDialog();
                if (savedialog.FileName.IndexOf(":") < 0) return; //被点了取消 
                //Microsoft.office.interop.excel.application xlapp = new microsoft.office.interop.excel.application();
                Microsoft.Office.Interop.Excel.Application xlapp = new Microsoft.Office.Interop.Excel.Application();
                if (xlapp == null)
                {
                    MessageBox.Show("可能您的机子未安装excel，无法创建excel对象！", "系统提示 ", 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 
                //定义表格内数据的行数和列数  
                int rowscount = mydgv.Rows.Count;
                int colscount = mydgv.Columns.Count;
                //行数不可以大于65536  
                if (rowscount > 65536)
                {
                    MessageBox.Show("数据行记录超过65536行，不能保存！", "系统提示 ", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    return;
                }
                //列数不可以大于255  
                if (colscount > 256)
                {
                    MessageBox.Show("数据列记录超过256列，不能保存！", "系统提示 ", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    return;
                }
                //写入标题
                for (int i = 0; i < mydgv.ColumnCount; i++)
                {
                    worksheet.Cells[1, i + 1] = mydgv.Columns[i].HeaderText;
                }
                //写入数值
                for (int r = 0; r < mydgv.Rows.Count; r++)
                {
                    for (int i = 0; i < mydgv.ColumnCount; i++)
                    {
                        if (mydgv[i, r].ValueType == typeof(string))
                        {
                            worksheet.Cells[r + 2, i + 1] = "" + mydgv.Rows[r].Cells[i].Value;//将长数值转换成文本
                        }
                        else
                        {
                            worksheet.Cells[r + 2, i + 1] = mydgv.Rows[r].Cells[i].Value;
                        }
                    }
                    System.Windows.Forms.Application.DoEvents();
                }
                worksheet.Columns.EntireColumn.AutoFit();//列宽自适应
                if (savedialog.FileName != "")
                {
                    try
                    {
                        workbook.Saved = true;
                        workbook.SaveCopyAs(savedialog.FileName);
                    }
                    catch (Exception ex)
                    {
                        MessageBox.Show("导出文件时出错,文件可能正被打开！..." + ex.Message, "系统提示 ", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    }

                }
                //GC.Collect();//强行销毁 
                MessageBox.Show("数据导出成功！ ", "提示信息", MessageBoxButtons.OK, MessageBoxIcon.Information);
                //关闭excel进程
                if (xlapp != null)
                {
                    xlapp.Quit();
                    System.Runtime.InteropServices.Marshal.ReleaseComObject(xlapp);
                    foreach (System.Diagnostics.Process theProc in System.Diagnostics.Process.GetProcessesByName("EXCEL"))
                    {
                        //先关闭图形窗口。如果关闭失败...有的时候在状态里看不到图形窗口的excel了， 
                        //但是在进程里仍然有EXCEL.EXE的进程存在，那么就需要杀掉它:p 
                        if (theProc.CloseMainWindow() == false)
                        {
                            theProc.Kill();
                        }
                    }
                    xlapp = null;
                }
            }
        }