private void btnClose_Click(object sender, EventArgs e)
        {
            ManageCourse cr = new ManageCourse();

            // this.Visible = false;
            this.Hide();
            cr.ShowDialog();
            this.Close();
        }
        private void btnCourses_Click(object sender, EventArgs e)
        {
            ManageCourse mCourse = new ManageCourse();

            //this.Visible = false;
            // mCourse.ShowDialog();
            this.Hide();
            mCourse.ShowDialog();
            this.Close();
        }