ScheduleWorks.UI.AddOrEditLessonForm.addAlternativeClassroomsButton_Click C# (CSharp) Method

        private void addAlternativeClassroomsButton_Click(object sender, EventArgs e)
        {
            List<ChooseItemsParameters> classrooms = new List<ChooseItemsParameters>();
            List<ChooseItemsParameters> alreadySelectedClassrooms = new List<ChooseItemsParameters>();
            foreach (var classroom in mDBManager.Classrooms)
            {
                if (long.Parse(dropDownListWantedRoom.SelectedValue.ToString()) != classroom.ID)
                {
                    classrooms.Add(new ChooseItemsParameters(classroom.Name, classroom.ShortName, classroom.ID));
                }
            }

            if (mFormState == FormState.AddingNew)
            {
                chooseAlternativeClassroomsForm = new ChooseItemsForm(ChooseItems.Mode.MultipleItems, "Избери алтернативни стаи за този урок", classrooms);
            }

            if(mFormState == FormState.Editing){
                foreach(var room in mLesson.AlternativeClassrooms){
                    alreadySelectedClassrooms.Add(new ChooseItemsParameters(room.Name, room.ShortName, room.ID));
                }

                chooseAlternativeClassroomsForm = new ChooseItemsForm(ChooseItems.Mode.MultipleItems, "Редактирай алтернативните стаи за този урок", classrooms, alreadySelectedClassrooms);
            }

            chooseAlternativeClassroomsForm.OnReadyButtonClicked += chooseAlternativeClassroomsForm_OnReadyButtonClicked;
            chooseAlternativeClassroomsForm.Show();
        }