private void Write_btn_Click(object sender, EventArgs e)
 {
     if ((saveFileDialog1.ShowDialog() == DialogResult.OK))
     {
         BadStud    s   = new BadStud(StudList);
         IO_Student std = new IO_Student(openFileDialog1.FileName);
         std.Write(s.GetBadStudList());
     }
 }
 private void Read_btn_Click(object sender, EventArgs e)
 {
     if ((openFileDialog1.ShowDialog() == DialogResult.OK))
     {
         IO_Student std = new IO_Student(openFileDialog1.FileName);
         std.Read();
         StudList = std.List_Sudent;
         DataGridViewUtils.ListStd_To_DGV(StudList, Student_DGV);
     }
 }