Solving System.NotSupportedException in Reactive Extensions with Dynamic Data

Описание: Learn how to troubleshoot and resolve the `System.NotSupportedException` error in Reactive Extensions while using Dynamic Data with C# . Explore effective strategies for managing background data operations.
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This video is based on the question https://stackoverflow.com/q/62542554/ asked by the user 'Pythoneer' ( https://stackoverflow.com/u/13628480/ ) and on the answer https://stackoverflow.com/a/62555713/ provided by the user 'Rich Bryant' ( https://stackoverflow.com/u/1061179/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem: System.NotSupportedException in Reactive Extensions

If you're diving into the world of Reactive Extensions (Rx) with Dynamic Data, you may have encountered a frustrating challenge: the dreaded System.NotSupportedException error from System.Reactive.dll. This issue tends to arise when you're trying to manage lists of data asynchronously with SourceList while also applying operations like filtering.

What often happens is that when the SourceList gets populated from a separate task or background thread, you have to deal with threading issues that lead to exceptions. This is especially common when you attempt to perform UI-bound actions on data that isn't coming from the UI thread.

What Are You Trying to Achieve?

In your case, you might be looking to accomplish two tasks:

Apply the Filter operation on the incoming data using TaskpoolScheduler.

Add data to SourceList from a background thread.

However, when the background task updates your SourceList, you run into the System.NotSupportedException error, necessitating the use of the Dispatcher Thread.

Steps to Fix the Issue

To resolve this issue, you'll want to ensure that the necessary operations are performed on the correct threads. Here’s a structured approach to achieving this:

1. Review Your Data Service

You have a BackroundDataService class that adds data to a SourceList. Ensure this service is properly designed to work with Rx and threading.

2. Adjust the Subscription Logic

Instead of directly observing on TaskpoolScheduler, you'll want to subscribe on MainThreadScheduler to ensure that data binding and any UI updates are executed on the main thread.

Recommended Code Adjustment

You should modify the connection setup for your BackroundDataService like so:

[[See Video to Reveal this Text or Code Snippet]]

Key Changes Explained

SubscribeOn: This operator is crucial because it specifies what thread your subscription should occur on. By using RxApp.MainThreadScheduler, you're ensuring that any binding to your UI happens on the main thread, preventing cross-thread exceptions.

ObserveOn: You can continue using TaskpoolScheduler for background data processing, allowing heavy tasks to not block the main thread.

Conclusion

By ensuring that your operations related to UI updates happen on the main thread, you can prevent the System.NotSupportedException from interrupting your workflow. Reactive Extensions offers powerful ways to handle data in a highly responsive manner, and understanding the threading contexts is key to effectively utilizing these tools.

For those facing similar issues or anyone looking to dive deeper into Rx and Dynamic Data, remember: threading is a fundamental aspect of building reactive applications. Proper handling will yield smoother, more efficient data management, giving you a robust application in the end.



By following this structured approach, you should be well on your way to avoiding System.NotSupportedException and harnessing the full power of Reactive Extensions with Dynamic Data. Happy coding!