// bind grids together
_flexRight.DataSource = _flexLeft;
_flexLeft.ScrollBars = ScrollBars.Horizontal;
            
// synchronize vertical scrolling 
// (this handles the AfterScroll event for both grids)
void flex_AfterScroll(object sender, C1.Win.C1FlexGrid.RangeEventArgs e)
{
    // update sender grid (could be _flexLeft or _flexRight)
    C1FlexGrid.C1FlexGrid src = ((C1FlexGrid)sender);
    src.Update();
    
    // get new vertical position from sender grid
    int y = src.ScrollPosition.Y;
    
    // apply new vertical position to the other grid
    if (src.Equals == _flexLeft)
    {
        _flexRight.ScrollPosition = new Point(_flexRight.ScrollPosition.X, y);
    }
    else
    {
        _flexLeft.ScrollPosition = new Point(_flexLeft.ScrollPosition.X, y);
    }
}