private void Add_button_Click(object sender, EventArgs e)
        {
            if (SelectedGroup_comboBox.SelectedValue != null)
            {
                ReloadTheoryLessons(Convert.ToInt32(SelectedGroup_comboBox.SelectedValue));
            }
            else
            {
                ReloadTheoryLessons(-1);
            }
            dataSet = BusinessLogic.ReadTheoryLessons();
            AddEditTheoryLessonForm AddTheoryLesson;

            if (SelectedGroup_comboBox.SelectedIndex != -1)
            {
                AddTheoryLesson = new AddEditTheoryLessonForm(dataSet.TheoryLessons, dataSet.Groups, dataSet.Auditoriums,
                                                              dataSet.Groups.Rows.Find(SelectedGroup_comboBox.SelectedValue), null);
            }
            else
            {
                AddTheoryLesson = new AddEditTheoryLessonForm(dataSet.TheoryLessons, dataSet.Groups, dataSet.Auditoriums, null, null);
            }
            AddTheoryLesson.Text = "Добавление теоретического занятия";
            this.Enabled         = false;
            AddTheoryLesson.ShowDialog();
            if (AddTheoryLesson.DialogResult == DialogResult.OK)
            {
                dataSet = BusinessLogic.WriteTheoryLessons(dataSet);
                if (SelectedGroup_comboBox.SelectedIndex != -1)
                {
                    ReloadTheoryLessons(Convert.ToInt32(SelectedGroup_comboBox.SelectedValue));
                }
            }
            this.Enabled = true;
        }
        private void Edit_button_Click(object sender, EventArgs e)
        {
            LastSelectionIndex = TheoryLessonsOfGroup_dGV.SelectedRows[0].Index;
            if (SelectedGroup_comboBox.SelectedValue != null)
            {
                ReloadTheoryLessons(Convert.ToInt32(SelectedGroup_comboBox.SelectedValue));
            }
            else
            {
                ReloadTheoryLessons(-1);
            }
            dataSet = BusinessLogic.ReadTheoryLessons();
            AddEditTheoryLessonForm EditTheoryLesson;

            if (SelectedGroup_comboBox.SelectedIndex != -1)
            {
                EditTheoryLesson = new AddEditTheoryLessonForm(dataSet.TheoryLessons, dataSet.Groups, dataSet.Auditoriums,
                                                               dataSet.Groups.Rows.Find(SelectedGroup_comboBox.SelectedValue),
                                                               dataSet.TheoryLessons.Rows.Find(TheoryLessonsOfGroup_dGV.SelectedRows[0].Cells["ID"].Value));
            }
            else
            {
                EditTheoryLesson = new AddEditTheoryLessonForm(dataSet.TheoryLessons, dataSet.Groups, dataSet.Auditoriums, null,
                                                               dataSet.TheoryLessons.Rows.Find(TheoryLessonsOfGroup_dGV.SelectedRows[0].Cells["ID"].Value));
            }
            EditTheoryLesson.Text = "Редактирование теоретического занятия";
            this.Enabled          = false;
            EditTheoryLesson.ShowDialog();
            if (EditTheoryLesson.DialogResult == DialogResult.OK)
            {
                dataSet = BusinessLogic.WriteTheoryLessons(dataSet);
                if (SelectedGroup_comboBox.SelectedIndex != -1)
                {
                    ReloadTheoryLessons(Convert.ToInt32(SelectedGroup_comboBox.SelectedValue));
                }
            }
            this.Enabled = true;
        }