private async Task StatisticBoard_UpdateView(object sender, EventArgs e)
{
await EFGenericRepository.SaveChangesAsync();
_statisticBoard.GroupsHistory = EFGenericRepository.GetWithLoad <GroupsHistory>().ToArray();
_statisticBoard.StudentsHistory = EFGenericRepository.GetWithLoad <StudentsHistory>().ToArray();
_statisticBoard.CountOfGroup = EFGenericRepository.CountOfEntities <Group>().ToString();
_statisticBoard.CountOfStudent = EFGenericRepository.CountOfEntities <Student>().ToString();
}