How to debug unexpected behavior in tree view navigation after implementing lazy loading and caching in Winforms and C#?

Question

I am creating a taxonomy as a tree view in Visual Studio Winforms with C#, which already holds some 40,000+ items in an SQLServer data base, and its nodes details are translated into 15 languages into a data grid. The latency for directly loading the collection as a hierarchy is not acceptable anymore.

I decided therefore to move to a lazy loading approach which has been quite effective. No latency to speak of.

But the navigation has gone wrong. Expanding the tree (I already have 8 levels of expansion) is not working reliably: expanding and collapsing both work as it should, when it works, but starting from the third level, the node selection can jump back to the top level without reason and then I have to expand again from the top down to where I was kicked off, etc.
My main issue is: how do I debug this? What are the events involved, apart from the NodeMouseClick?
I do not think this behavior is reproducible because of the large database size involved. The code is also quite large, but more to the point, I do not where in the code the error is taking place.

What is the request? How do I debug navigating a tree view which misbehaves? I would be quite capable of identifying logic and programming errors by myself, if I can identify where the issue takes place.

Answer 1

Hi @Yves Chaix , Welcome to Microsoft Q&A,

Since your problem cannot be reproduced, I can only give you some suggestions.

1. When debugging, in addition to NodeMouseClick, you can also pay attention to the following tree view-related events to confirm whether the tree view navigation is abnormal due to the triggering of other events:

• BeforeExpand and AfterExpand: can help you track the behavior of nodes before and after expansion.
• BeforeSelect and AfterSelect: these events are triggered when node selection occurs, suitable for checking whether the selection is as expected.
• NodeMouseDoubleClick: if the user double-clicks the node, this event will also be triggered.

1. Through these events, you can insert logging in the callback method to record the event triggering information to the debug console or file to analyze and reproduce the problem.
2. Use Console.WriteLine or Debug.WriteLine to output detailed debugging information, such as the current node's Name, Level, parent node, etc., to record the status when the event is triggered.
3. To avoid printing too much information in the console, you can consider logging information only for specific levels (such as the third level and above), which can narrow the scope of investigation.
4. Set a custom property on each node to mark information such as level, loading status, etc., so as to confirm the correctness of the node status during debugging. For example, you can use the Tag property to mark the level or loaded status of the node.
5. In each node loading or click event, check whether the value of the Tag property is correct, and ensure that the logic of lazy loading does not repeat or misoperate nodes of other levels.
6. If you use multithreading or asynchronous operations to load node data, ensure that all operations accessing the tree view are performed on the main thread. Accessing UI controls on non-main threads can cause unexpected behavior.
7. You can use Invoke or BeginInvoke to ensure that the code is executed on the main thread to avoid non-main threads modifying the tree view.
8. Sometimes clicking nodes in rapid succession can cause UI operation lags. You can add a shorter delay to the selection event to avoid interference from consecutive clicks, such as Task.Delay(100), to ensure that the selection operations are performed in order.

Best Regards,

Jiale

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