private void toDoListView_DoubleClick(object sender, EventArgs e)
        {
            if (toDoListView.SelectedItems.Count < 1)
            {
                return;
            }

            ListViewItem selectedItem = toDoListView.SelectedItems[0];

            TaskEditorForm taskEditorForm = new TaskEditorForm();

            Task task = new Task()
            {
                DateTimeByExecute = DateTime.Parse(selectedItem.SubItems[0].Text),
                Title             = selectedItem.SubItems[1].Text
            };

            DialogResult dialogResult = taskEditorForm.ShowDialog(task);

            if (dialogResult == DialogResult.OK)
            {
                selectedItem.SubItems[0].Text = taskEditorForm.ChangedTask.DateTimeByExecute.ToString();
                selectedItem.SubItems[1].Text = taskEditorForm.ChangedTask.Title;
            }
        }
        private void addTaskButton_Click(object sender, EventArgs e)
        {
            TaskEditorForm taskEditorForm = new TaskEditorForm();

            DialogResult dialogResult = taskEditorForm.ShowDialog();

            if (dialogResult == DialogResult.OK)
            {
                ListViewItem item = new ListViewItem();
                item.SubItems[0].Text = taskEditorForm.ChangedTask.DateTimeByExecute.ToString();
                item.SubItems.Add(taskEditorForm.ChangedTask.Title);
                toDoListView.Items.Add(item);
            }
        }