private void UpdateId_Click(object sender, EventArgs e) { if (idTextBox.Text != "") { long id = 0; if (long.TryParse(idTextBox.Text, out id)) { ItemBase[] items = new ItemBase[itemBox.Items.Count]; itemBox.Items.CopyTo(items, 0); if (items.FirstOrDefault(x => x.ItemId == id && x.ItemId != (itemBox.SelectedItem as ItemBase).ItemId) != null) { Interaction.MsgBox("ID already in use", MsgBoxStyle.Exclamation); idTextBox.Text = ""; } else { idLabel.Text = idTextBox.Text; idTextBox.Text = ""; } } else { Interaction.MsgBox("ID must be a number.", MsgBoxStyle.Exclamation); idTextBox.Text = ""; } } }