How to Safely Update an ObservableCollection from a Background Thread in .NET 4.5?

Updating ObservableCollection from a Background Thread: A .NET 4.5 Approach

The Challenge: Thread Safety with ObservableCollection

Directly modifying an ObservableCollection from a worker thread in WPF applications throws exceptions. This is a consequence of WPF's threading model, designed to maintain UI responsiveness during background tasks.

The .NET 4.5 Solution: BindingOperations.EnableCollectionSynchronization

.NET 4.5 introduces a streamlined solution: BindingOperations.EnableCollectionSynchronization. Called from the UI thread, this method:

• Ensures that CollectionChanged events are marshaled back to the UI thread.
• Implements locking to prevent race conditions while handling these events on the UI thread.

Important Considerations for Thread Safety

While EnableCollectionSynchronization significantly improves thread safety, developers must still adhere to best practices:

1. Consistent Locking: Maintain consistent locking when modifying the ObservableCollection, using the same mechanism passed to EnableCollectionSynchronization.
2. Appropriate Locking Mechanism: Select the most suitable locking mechanism – a simple lock statement often suffices, but custom synchronization might be necessary in complex scenarios.
3. Passing the Synchronization Context: Correctly pass the lock object or synchronization callback to EnableCollectionSynchronization is crucial for proper functionality. Failure to do so can lead to unexpected behavior.

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