void DetachDocument ()
{
if (document == null)
return;
document.BeginUndo -= OnBeginUndo;
document.EndUndo -= OnEndUndo;
document.Undone -= DocumentHandleUndone;
document.Redone -= DocumentHandleRedone;
document.LineChanged -= HandleDocLineChanged;
document.TextReplaced -= HandleTextReplaced;
document.TextSet -= HandleDocTextSet;
document.Folded -= HandleTextEditorDataDocumentFolded;
document.FoldTreeUpdated -= HandleFoldTreeUpdated;
document = null;
}