Disable expanding after doubleclick

There is no simple way to achieve this, as far as I know. One thought would be to have a bool variable set to true on the DoubleClick event, and use the e.Cancel property of the BeforeExpand event to prevent the node from expanding. However, those two events are fired in the opposite order, so that is not a solution. I don't have another solution from the top of my head; will update if I come up with one.

Update

I have played around with this a bit, and I have found one way that works reasonably well. As I have mentioned the problem is that BeforeExpand happens before DoubleClick, so we can't set any state in DoubleClick to use in BeforeExpand.

We can, however, detect (potential) double clicks in another way: by measuring the time between MouseDown events. If we get two MouseDown events within the time period that defines a double click (as stated in SystemInformation.DoubleClickTime), it should be a double click, right? And the MouseDown event is raised before BeforeExpand. So, the following code works rather well:

private bool _preventExpand = false;
private DateTime _lastMouseDown = DateTime.Now;

private void treeView1_BeforeExpand(object sender, TreeViewCancelEventArgs e)
{
    e.Cancel = _preventExpand;
    _preventExpand  = false;
}

private void treeView1_MouseDown(object sender, MouseEventArgs e)
{
    int delta = (int)DateTime.Now.Subtract(_lastMouseDown).TotalMilliseconds;            
    _preventExpand = (delta < SystemInformation.DoubleClickTime);
    _lastMouseDown = DateTime.Now;
}

I say "rather well" because I feel that it prevents the node from expanding in some cases when it should not (for instance if you within the double click time click first on the node text and then on the plus sign). That might be possible to solve in some way, or perhaps you can live with that.

private bool isDoubleClick = false;

private void treeView1_BeforeCollapse(object sender, TreeViewCancelEventArgs e)
{
    if (isDoubleClick && e.Action == TreeViewAction.Collapse)
        e.Cancel = true;
}

private void treeView1_BeforeExpand(object sender, TreeViewCancelEventArgs e)
{
    if (isDoubleClick && e.Action == TreeViewAction.Expand)
        e.Cancel = true;
}

private void treeView1_MouseDown(object sender, MouseEventArgs e)
{
    isDoubleClick = e.Clicks > 1;
}

You can declare a private field isDoubleClick and set various TreeView events as above. This will prevent expand/collapse TreeView node on double click. However expand/collapse will work via + and - icons.

A MouseDown event will occur before the BeforeExpand/BeforeCollapse events. You can check the Clicks property of the MouseEventArg to distinguish between a double-click and a single click:

bool dblClick;

private void treeView_MouseDown(object sender, MouseEventArgs e)
{
  dblClick = e.Button == MouseButtons.Left && e.Clicks == 2;
}

private void treeView_BeforeExpand(object sender, TreeViewCancelEventArgs e)
{
  if (e.Action == TreeViewAction.Expand) e.Cancel = dblClick;
}