private void btnSave_Click(object sender, EventArgs e)
 {
     if (!string.IsNullOrEmpty(txtRequestContent.Text))
     {
         string  content = txtRequestContent.Text;
         Request hp      = new Request(s.StuID, DateTime.Now.ToString(), content, "", "", "", 1);
         RequestDAO.Insert(hp);
         MessageBox.Show("Request Success");
         DataTable dt     = RequestDAO.GetDataTableByStuID(s.StuID);
         DataView  dv     = new DataView(dt);
         string    filter = "";
         if (comboBox1.SelectedIndex == 0)
         {
             filter = "maID is not null";
         }
         if (comboBox1.SelectedIndex == 1)
         {
             filter = "maID is null";
         }
         dv.RowFilter              = filter;
         dataGridView1.DataSource  = dv;
         btnSave.Enabled           = false;
         txtRequestContent.Enabled = false;
         txtRequestContent.Text    = "";
         btnCancel.Enabled         = false;
         btnRequest.Enabled        = true;
     }
     else
     {
         MessageBox.Show("TextFiled is not empty");
     }
 }