private void menuEdit_DropDownOpening(object sender, EventArgs e)
{
DoInActiveTextBox(ctrl =>
{
this.menuUndo.Enabled = ctrl.CanUndo;
// 検索対象は本文入力のみ
var istestBody = ctrl.Name == "textBody";
menuFind.Enabled = istestBody;
menuReplace.Enabled = istestBody;
this.menuSelectAll.Enabled = ctrl.Text.Length > 0;
var isctrlSelected = ctrl.SelectionLength > 0;
this.menuCut.Enabled = isctrlSelected;
this.menuCopy.Enabled = isctrlSelected;
this.menuDelete.Enabled = isctrlSelected;
});
// クリップボードの内容確認
this.menuPaste.Enabled = Clipboard.ContainsData(DataFormats.Text);
}