private void добавитьToolStripMenuItem_Click(object sender, EventArgs e)
        {
            var frmThingInsert = new UpsertThingFrm(UpsertThingFrm.State.Insert);

            if (frmThingInsert.ShowDialog() == DialogResult.OK)
            {
                AddThing(frmThingInsert.Weight, frmThingInsert.Cost);
            }
        }
        private void изменитьToolStripMenuItem_Click(object sender, EventArgs e)
        {
            if (lvThing.SelectedItems.Count == 0)
            {
                return;
            }
            var frmThingUpdate = new UpsertThingFrm(UpsertThingFrm.State.Update);
            var selectedItem   = lvThing.SelectedItems[0];

            frmThingUpdate.Weight = selectedItem.SubItems[1].Text;
            frmThingUpdate.Cost   = selectedItem.SubItems[2].Text;
            if (frmThingUpdate.ShowDialog() == DialogResult.OK)
            {
                selectedItem.SubItems[1].Text = frmThingUpdate.Weight;
                selectedItem.SubItems[2].Text = frmThingUpdate.Cost;
            }
        }