private void dodajZadanieButton_Click(object sender, EventArgs e)
        {
            using (addEditWindow addWindowObj = new addEditWindow("Dodaj zadanie"))
            {
                if (addWindowObj.ShowDialog() == DialogResult.OK)
                {
                    String[]     dataFromAddWindow = addWindowObj.commWithMainWindow;
                    ListViewItem newLVItem         = new ListViewItem(dataFromAddWindow);
                    listView1.Items.Add(newLVItem);
                    aplication.addTask(int.Parse(dataFromAddWindow[1]), int.Parse(dataFromAddWindow[2]), int.Parse(dataFromAddWindow[3]), int.Parse(dataFromAddWindow[4]), int.Parse(dataFromAddWindow[5]));

                    usunWszystkieZadaniaButton.Visible = true;
                    wyswietlHarmonogramButton.Visible  = true;
                    wyswietlPlanPracyButton.Visible    = true;
                }
            }
        }
        private void edytujZadanieButton_Click(object sender, EventArgs e)
        {
            ListViewItem wybrane = listView1.SelectedItems[0];

            String[] existingData = { wybrane.SubItems[0].Text, wybrane.SubItems[1].Text, wybrane.SubItems[2].Text, wybrane.SubItems[3].Text, wybrane.SubItems[4].Text, wybrane.SubItems[5].Text };
            using (addEditWindow editWindowObj = new addEditWindow("Edytuj zadanie", existingData))
            {
                if (editWindowObj.ShowDialog() == DialogResult.OK)
                {
                    String[] dataFromEditWindow = editWindowObj.commWithMainWindow;
                    for (int i = 0; i < dataFromEditWindow.Length; i++)
                    {
                        listView1.SelectedItems[0].SubItems[i].Text = dataFromEditWindow[i];
                    }
                    aplication.addTask(int.Parse(dataFromEditWindow[1]), int.Parse(dataFromEditWindow[2]), int.Parse(dataFromEditWindow[3]), int.Parse(dataFromEditWindow[4]), int.Parse(dataFromEditWindow[5]));
                }
            }
        }