private void CollectionInfoForm_Load(object sender, EventArgs e)
        {
            lblCollectionName.Text        = Control.currentCollection.Name;
            lblCollectionDescription.Text = Control.currentCollection.Description;
            lblCreatingDate.Text          = Control.currentCollection.CreatingDate.ToShortDateString();
            lblAverageMark.Text           = Control.currentCollection.AverageMark.ToString();
            cbMark.SelectedIndex          = 4;

            CompleteForm.dgvCollectionComments(this);
            CompleteForm.dgvCollectionCreators(this);
            CompleteForm.dgvCollectionObjects(this);
            CompleteForm.dgvCollectionCategories(this);
            CompleteForm.dgvCollectionMarks(this);
        }
        private void btnAddMark_Click(object sender, EventArgs e)
        {
            if (cbMark.Text.Length == 0)
            {
                Control.Exclamation("Оценка не выбрана.", "Оценка");
                return;
            }
            if (Control.currentCollection.Marks.ToList().Exists(x => x.User == Control.currentUser))
            {
                Control.Exclamation("Вы уже ставили оценку этой коллекции.", "Оценка");
                return;
            }

            Mark newMark = new Mark();

            newMark.Value      = int.Parse(cbMark.Text);
            newMark.User       = Control.currentUser;
            newMark.Collection = Control.currentCollection;

            Control.container.Marks.Add(newMark);

            Control.currentCollection.Marks.Add(newMark);
            Control.currentCollection.AverageMark =
                (double)(from mark in Control.currentCollection.Marks select mark.Value).Sum() /
                (double)Control.currentCollection.Marks.Count;

            Collection changingCollection = new Collection();

            changingCollection             = Control.container.Collections.Find(Control.currentCollection.Id);
            changingCollection.AverageMark = Control.currentCollection.AverageMark;

            Control.container.SaveChanges();

            CompleteForm.dgvCollectionMarks(this);
            lblAverageMark.Text = Control.currentCollection.AverageMark.ToString();
        }