private void addButton_Click(object sender, EventArgs e)
 {
     var dialog = new InputExtensionDialog();
     if (dialog.ShowDialog(this) == DialogResult.OK)
     {
         ListViewItem item = new ListViewItem(new[] {
             String.Empty, dialog.Filter.ExtensionsString, dialog.Filter.Description
         });
         extensionsView.Items.Add(item);
     }
 }
        private void editButton_Click(object sender, EventArgs e)
        {
            var item = extensionsView.SelectedItems.Cast<ListViewItem>().DefaultIfEmpty(null).First();
            if (item == null)
            {
                MessageBox.Show(this, "項目が選択されていません。", this.Text,
                    MessageBoxButtons.OK, MessageBoxIcon.Warning);
                return;
            }

            var filter = new ExtensionFilter(false, item.SubItems[1].Text, item.SubItems[2].Text);
            var dialog = new InputExtensionDialog(filter);
            if (dialog.ShowDialog(this) == DialogResult.OK)
            {
                item.SubItems[1].Text = dialog.Filter.ExtensionsString;
                item.SubItems[2].Text = dialog.Filter.Description;
            }
        }