private void btnAdd_Click(object sender, EventArgs e)
        {
            if (ValidField())
            {
                MessageBox.Show("Please fill out all textbox!", "Infomation", MessageBoxButtons.OK, MessageBoxIcon.Information);
                return;
            }
            Class Class = new Class(txtClassID.Text, txtClassName.Text, cmbFacultyID.SelectedValue.ToString());

            if (obj.Class_Insert(Class))
            {
                MessageBox.Show("Insert Class successed!", "Infomation", MessageBoxButtons.OK, MessageBoxIcon.Information);
                BinData();
                Clear();
            }
            else
            {
                MessageBox.Show("Insert Class unsuccessed!", "Infomation", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
        }