private void btnUpdate_Click(object sender, EventArgs e)
        {
            if(SelectedIndex != -1)
            {
                LicenseEditor editor = new LicenseEditor(SelectedItemTag as License);

                if (DialogResult.OK == editor.ShowDialog())
                    RefreshListItems();
            }
        }
        private void btnAdd_Click(object sender, EventArgs e)
        {
            LicenseEditor editor = new LicenseEditor();

            if (DialogResult.OK == editor.ShowDialog())
                RefreshListItems();
        }