How to ensure that adjusting a TrackBar control with a mouse will set values multiple of SmallChange and not any in between?

问题

I used .Net trackbar control. My trackbar point is 0...5...10..15. Problem is, when user scrolled trackbar they easily drop scroll in between points. But i wan't to that user only drop the scroll in my display point only. like they set only 0,5,10 etc. Not they set 6,7,8,9...

I set SmallChanges property with 5 value. But they working with keyboard changes not with mouse scrolling.

回答1:

You can simply force the Value property to be a multiple of the SmallChange property by overriding its value in an event handler for the ValueChanged event. Like this:

    private void trackBar1_ValueChanged(object sender, EventArgs e) {
        var bar = (TrackBar)sender;
        if (bar.Value % bar.SmallChange != 0) {
            bar.Value = bar.SmallChange * ((bar.Value + bar.SmallChange / 2) / bar.SmallChange);
        }
    }

Note that this even works while the user is dragging the thumb with the mouse, like it behaves when he uses the keyboard. I assumed that's what you wanted.

来源：https://stackoverflow.com/questions/18634269/how-to-ensure-that-adjusting-a-trackbar-control-with-a-mouse-will-set-values-mul