private void btnNew_Click(object sender, EventArgs e)
 {
     var newForm = new FrmProfessor();
     newForm.MdiParent = this.MdiParent;
     this.Close();
     newForm.Show();
 }
        private void professoresToolStripMenuItem_Click(object sender, EventArgs e)
        {
            this.CloseActiveWindow();

            var frmProfessor = new FrmProfessor();
            frmProfessor.MdiParent = this;
            frmProfessor.Show();
        }
        private void dgProfessors_CellContentDoubleClick(object sender, DataGridViewCellEventArgs e)
        {
            var cell = dgProfessors[0, e.RowIndex];
            var professorId = Convert.ToInt32(cell.Value);

            if (professorId > 0)
            {
                var frmProfessor = new FrmProfessor(professorId);
                frmProfessor.MdiParent = this.MdiParent;
                frmProfessor.Show();

                this.Close();
            }
        }