private void toolStripLabel4_Click(object sender, EventArgs e)

        {

            SaveFileDialog saveFileDialog = new SaveFileDialog();

            saveFileDialog.Filter = "Execl文件(*.xls)
------解决方案--------------------
*.xls";

            saveFileDialog.FilterIndex = 0;

            saveFileDialog.RestoreDirectory = true;

            saveFileDialog.CreatePrompt = true;

            saveFileDialog.Title = "数据视图导出EXCEL文件"; 

            saveFileDialog.ShowDialog();

            Stream myStream;

            myStream = saveFileDialog.OpenFile();

            StreamWriter sw = new StreamWriter(myStream, System.Text.Encoding.GetEncoding("utf-8"));

            string str = "";

            DateTime start = DateTime.Now;

            try

            {

                //写标题

                for (int i = 0; i < dataGridView1.ColumnCount; i++)

                {

                    if (i > 0)

                    {

                        str += "\t";

                    }

                    str += dataGridView1.Columns[i].HeaderText;

                }

                sw.WriteLine(str);



                //写内容

                 for (int j = 0; j < dataGridView1.Rows.Count; j++)