private void PrevClick(object sender, EventArgs e) { TVRequestInfo header1 = _source.GetPrevious(ref _currFirstIndex); TVRequestInfo header2 = _source.GetPrevious(ref _currSecondIndex); _currFirstDiffIndex = -1; _currSecondDiffIndex = -1; if (header1 != null && header2 != null) { if (!_buttonNext.Enabled) { _buttonNext.Enabled = true; } DoDiff(_currFirstIndex, _currSecondIndex); } else { _buttonPrev.Enabled = false; } }