private void addStudentsToolStripMenuItem_Click(object sender, EventArgs e)
        {
            Add_Students addstd = new Add_Students();

            addstd.MdiParent = this;
            addstd.Show();
            addstd.Activate();
        }
        private void button1_Click(object sender, EventArgs e)
        {
            int res = bl.Add_Student(textBox1.Text, textBox2.Text, textBox3.Text, textBox4.Text, textBox5.Text, dateTimePicker1.Text, textBox7.Text, textBox6.Text, richTextBox1.Text);

            MessageBox.Show("Student Details Registered Success");

            Add_Students add = new Add_Students();

            add.Show();
            this.Hide();
        }