private void CargarGrilla()
{
dgvAlumno.DataSource = alumno.ListarAlumnos();
dgvAlumno.SelectionMode = DataGridViewSelectionMode.FullRowSelect;
dgvAlumno.AutoSizeColumnsMode = DataGridViewAutoSizeColumnsMode.AllCells;
dgvAlumno.AllowUserToAddRows = false;
dgvAlumno.AllowUserToDeleteRows = false;
dgvAlumno.ReadOnly = true;
}