C#导出Excel速度慢的解决方案,该怎么解决

C#导出Excel速度慢的解决方案
C#导出Excel速度奇慢，大概要5分钟时间，这个怎么解决

[解决办法]
测试导出速度超快滴：
源码：

C# code

        private void toolStripLabel4_Click(object sender, EventArgs e)        {            SaveFileDialog saveFileDialog = new SaveFileDialog();            saveFileDialog.Filter = "Execl文件(*.xls)|*.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++)                 {                     string tempStr = "";                     for (int k = 0; k < dataGridView1.Columns.Count; k++)                     {                         if (k > 0)                         {                             tempStr += "\t";                         }                         if (dataGridView1.Rows[j].Cells[k].Value == null)                         {                             tempStr += string.Empty;                         }                         else                         {                             tempStr += dataGridView1.Rows[j].Cells[k].Value.ToString();                         }                     }                     sw.WriteLine(tempStr);                                     }                 sw.Close();                 myStream.Close();            }            catch(Exception ex)            {                MessageBox.Show(ex.Message);            }            finally            {                sw.Close();                myStream.Close();            }            MessageBox.Show("将此工作表导出为excel共耗时：" + DateTime.Now.Subtract(start).TotalMilliseconds.ToString() + "毫秒");        }