超难！edit输入限制问题？部份只读?

delphi下实现很简单哈，响应Onchange事件就可以老
const
  EDT_MAXLENGTH = 6;

procedure TForm1.AfterConstruction();
begin
  inherited AfterConstruction();
  fStaticStr := 'abc';
  Edit1.MaxLength := EDT_MAXLENGTH;
  Edit1.Text := fStaticStr;
end;
// -----------------------------------------------------------------------------

procedure TForm1.Edit1Change(Sender: TObject);
begin
  if not AnsiStartsText(fStaticStr, Edit1.Text) then
  begin
    Edit1.Text := fStaticStr;
    Edit1.SelStart := Length(fStaticStr);
    Beep();
  end;
end;

精妙的思路,学习了