Question

I’m having a seriously annoying problem on which I’ve been spending a ridiculous amount of time on trying to resolved and still to no avail!!

Over the years, I’ve never used the standard treeview that comes with .NET as I’ve always used a third-party component but talking about a bad experience so far!!!

In short, I’m loading my drives and then when expanding a drive, I list folders, and so on… Nothing new here, but I’m having 2 major problems:

1. When all branches are collapsed, it triggers the before and after expand event twice.. BeforeExpand x 2, then AfterExpand x 2.

2. When multiple branches are expanded, it will trigger the event 2 for each expanded branches… It’s like I’m calling some sort of recursive code when I’m not… So for example,

Expand C -> Triggers BeforeExpand x 2, then AfterEvent x 2 – Leave it expanded

Expand E -> Triggers BeforeExpand x 2 for E, then AfterEvent x 2, then does it again for C – Leave E expanded.

Expand F -> Triggers BeforeExpand x 2 for F, then AfterEvent x 2, then does it again for E then C.

It doesn’t make sense!!

Code wise:

1. Initialize the BeforeExpand and AfterExpand when my form initializes i.e.

       treeView1.BeforeExpand += new TreeViewCancelEventHandler(treeView1_BeforeExpand);
       treeView1.AfterExpand += new TreeViewEventHandler(treeView1_AfterExpand);
   

2. When I expand a node, a background thread is called and either loads the drives or folders. From the background worker thread, I call a function, which handles the cross threading issue by calling a delegate so again, nothing special

I’m out of ideas as to what’s causing this bar the fact that it could be a bug on MS side, but I doubt it… It feels like a problem that just far too obvious.

I’m happy to post my code if needed as this was just a dummy test app I started and maybe you’ll spot something I’ve done wrong but I just can’t see what.

Hope someone has a clue as to what’s causing this.

Thanks.

Thierry.

Answer 1

I figured out what the problem was so I thought I’d share it in case this happens to anyone else!!

This is insane but in the background worker thread, I called the treeview1.Sort() in the RunWorkerCompleted and this is what is causing the beforeExpand and afterExpand events to be called multiple times! Once removed, it behaved accordingly.

I guess I will sort the folders first and then raised the delegate from the thread to update the UI with the sorted list.

That’s it!