private void Edit_button_Click(object sender, EventArgs e)
        {
            LastSelectionIndexInPracticeLessons = PracticeLessonsOfStudent_dGV.SelectedRows[0].Index;
            dataSet = BusinessLogic.ReadPracticeLessons();
            AddEditPracticeLessonForm EditPracticeLesson;

            EditPracticeLesson = new AddEditPracticeLessonForm(dataSet.PracticeLessons, dataSet.Students, null,
                                                               dataSet.PracticeLessons.Rows.Find(PracticeLessonsOfStudent_dGV.SelectedRows[0].Cells["ID"].Value));
            EditPracticeLesson.Text = "Редактирование практического занятия";
            this.Enabled            = false;
            EditPracticeLesson.ShowDialog();
            if (EditPracticeLesson.DialogResult == DialogResult.OK)
            {
                dataSet = BusinessLogic.WritePracticeLessons(dataSet);
                ReloadPracticeLessonsNeedsForReplacement();
            }
            this.Enabled = true;
        }
        private void Edit_button_Click(object sender, EventArgs e)
        {
            LastSelectionIndexInPracticeLessons = PracticeLessonsOfStudent_dGV.SelectedRows[0].Index;
            if (SelectedStudent_comboBox.SelectedValue != null)
            {
                ReloadPracticeLessons(Convert.ToInt32(SelectedStudent_comboBox.SelectedValue));
            }
            else
            {
                ReloadPracticeLessons(-1);
            }
            dataSet = BusinessLogic.ReadPracticeLessons();
            AddEditPracticeLessonForm EditPracticeLesson;

            if (SelectedStudent_comboBox.SelectedIndex != -1)
            {
                EditPracticeLesson = new AddEditPracticeLessonForm(dataSet.PracticeLessons, dataSet.Students,
                                                                   dataSet.Students.Rows.Find(SelectedStudent_comboBox.SelectedValue),
                                                                   dataSet.PracticeLessons.Rows.Find(PracticeLessonsOfStudent_dGV.SelectedRows[0].Cells["IDPLColumn"].Value));
            }
            else
            {
                EditPracticeLesson = new AddEditPracticeLessonForm(dataSet.PracticeLessons, dataSet.Students, null,
                                                                   dataSet.PracticeLessons.Rows.Find(PracticeLessonsOfStudent_dGV.SelectedRows[0].Cells["IDPLColumn"].Value));
            }
            EditPracticeLesson.Text = "Редактирование практического занятия";
            this.Enabled            = false;
            EditPracticeLesson.ShowDialog();
            if (EditPracticeLesson.DialogResult == DialogResult.OK)
            {
                dataSet = BusinessLogic.WritePracticeLessons(dataSet);
                if (SelectedStudent_comboBox.SelectedIndex != -1)
                {
                    ReloadPracticeLessons(Convert.ToInt32(SelectedStudent_comboBox.SelectedValue));
                }
            }
            this.Enabled = true;
        }
        private void Add_button_Click(object sender, EventArgs e)
        {
            if (SelectedStudent_comboBox.SelectedValue != null)
            {
                ReloadPracticeLessons(Convert.ToInt32(SelectedStudent_comboBox.SelectedValue));
            }
            else
            {
                ReloadPracticeLessons(-1);
            }
            dataSet = BusinessLogic.ReadPracticeLessons();
            AddEditPracticeLessonForm AddPracticeLesson;

            if (SelectedStudent_comboBox.SelectedIndex != -1)
            {
                AddPracticeLesson = new AddEditPracticeLessonForm(dataSet.PracticeLessons, dataSet.Students,
                                                                  dataSet.Students.Rows.Find(SelectedStudent_comboBox.SelectedValue),
                                                                  null);
            }
            else
            {
                AddPracticeLesson = new AddEditPracticeLessonForm(dataSet.PracticeLessons, dataSet.Students, null, null);
            }
            AddPracticeLesson.Text = "Добавление практического занятия";
            this.Enabled           = false;
            AddPracticeLesson.ShowDialog();
            if (AddPracticeLesson.DialogResult == DialogResult.OK)
            {
                dataSet = BusinessLogic.WritePracticeLessons(dataSet);
                if (SelectedStudent_comboBox.SelectedIndex != -1)
                {
                    ReloadPracticeLessons(Convert.ToInt32(SelectedStudent_comboBox.SelectedValue));
                }
            }
            this.Enabled = true;
        }