private void buttonInfo_Click(object sender, EventArgs e)
 {
     try
     {
         FormBookExemplar newForm =
             new FormBookExemplar(Int32.Parse(dataGridViewB.CurrentRow.Cells[0].Value.ToString()));
         newForm.ParentAdminMainMenu = this;
         newForm.Show();
         Hide();
     }
     catch (NullReferenceException)
     {
         MessageBox.Show("Строка не выбрана");
     }
 }