Hi,

I tried this out and I am seeing similar results, although it's not always just the mouse wheel. If I click and drag the thumb, the tree doesn't seem to fire the Scroll event to reflect the current TopNode until I release the mouse sometimes.It's not always consistent.

This appears to be a bug in the tree.So I'm going to ask Infragistics Developer Support to create a case for you and write this up as a bug for developer review.

Your workaround seems okay, except that you are not honoring the delta. For example, if Delta is 3, you are only going to scroll one node at a time. Also... since you are not cancelling the MouseWheel event, I would think that this code would cause the tree to scroll double - once because you are telling it to and again because of the built-in handling of the mouse wheel.

I have been able to do something but I wander if it is "legit"!

When I detect a MouseWheel event, I handle it, set my other tree TopNode and cancelled the Scroll event that occurs right after.

Would there be another (better) way of doing it?

private bool _ignoreNextScroll;

void treeHeadersLeft_MouseWheel(object sender, MouseEventArgs e)
{
	bool up = e.Delta > 0;
	ScrollTree(treeHeadersLeft, treeHeadersRight, up);
}

void treeHeadersRight_MouseWheel(object sender, MouseEventArgs e)
{
	bool up = e.Delta > 0;
	ScrollTree(treeHeadersRight,treeHeadersLeft,up);
}

private void ScrollTree(UltraTree treeActive, UltraTree treePassive, bool up)
{
	_ignoreNextScroll = true;

	UltraTreeNode topNode = treeActive.TopNode;
	if (topNode == null)
		return;

	UltraTreeNode newTopNode = topNode.NextVisibleNode;
	newTopNode = up ? topNode.PrevVisibleNode : topNode.NextVisibleNode;

	if (newTopNode != null)
		treePassive.TopNode = newTopNode;
}

void treeHeadersRight_Scroll(object sender, TreeScrollEventArgs e)
{
	if (_ignoreNextScroll)
	{
		_ignoreNextScroll = false;
		return;
	}
	treeHeadersLeft.TopNode = treeHeadersRight.TopNode;
}

void treeHeadersLeft_Scroll(object sender, TreeScrollEventArgs e)
{
	if (_ignoreNextScroll)
	{
		_ignoreNextScroll = false;
		return;
	}
	treeHeadersRight.TopNode = treeHeadersLeft.TopNode;
}

TopNode is working correctly when I use the thumbs on the scrollbars.

But I use the mouse wheel to scroll, then my ultratrees become offset by 1 element. It appears that TopNode is set to the current item and not the new item. I also tried the MouseWheel event but it has the same behavior. Any ideas?

Sorry, it's TopNode, not FirstNode. It's on the tree control itself.