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Learn how to fix issues with the `CollectionView` in Xamarin Forms when it fails to update properly with new items in Observable Collections.
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This video is based on the question https://stackoverflow.com/q/65897565/ asked by the user 'Sawan' ( https://stackoverflow.com/u/13670102/ ) and on the answer https://stackoverflow.com/a/65897725/ provided by the user 'puko' ( https://stackoverflow.com/u/2941906/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving Xamarin Forms CollectionView Not Updating with New Observable Collection Items

When developing applications with Xamarin Forms, you might encounter an issue where the CollectionView does not refresh or display the updated data from an ObservableCollection as expected. Specifically, you might find that when you add new items, especially at the beginning of your list, the display becomes distorted, removing prior items and only showing the latest entry. In this guide, we’ll break down your problem and provide a clear solution that ensures your CollectionView updates seamlessly with new data.

Understanding the Problem

In the scenario presented, the developer faced an issue with their CollectionView where it only displayed the latest message and distorted the UI upon updating the ObservableCollection. This issue typically arises when the ItemSource of the CollectionView is reset instead of simply updating the existing ObservableCollection.

Common Symptoms:

The CollectionView shows only one item.

Items are removed from view when new items are added.

The correct list appears only after navigating away and back to the page.

The Solution

To resolve the issue where your CollectionView does not refresh properly, follow these steps:

1. Avoid Resetting the ItemSource

The root cause of the problem lies in the line of code where the ItemSource is reassigned:

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

By reassigning the ItemSource, you are telling the CollectionView to redraw the entire list. Instead, you should only update the ObservableCollection.

2. Directly Update the ObservableCollection

Instead of resetting the ItemSource, add new items directly to your ObservableCollection. For example, if you're inserting a new message, your code should resemble the following:

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

In this way, you maintain the connection to the CollectionView, and it will automatically reflect the changes in the UI. The ObservableCollection will notify the UI when items are added or removed.

3. Implementing the Change in Code

Here is an example of what your updated data handling methods might look like:

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4. A Simple Example

To further illustrate, here’s a simplified example of how to set up your CollectionView properly:

XAML Setup

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Code Behind

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Conclusion

By following these straightforward steps and avoiding the reassignment of the ItemSource, you can ensure that your Xamarin Forms CollectionView updates correctly as items are added to your ObservableCollection. This not only improves the user experience but also streamlines the performance of your application.

If you have any further questions or experiences with Xamarin Forms, feel free to share in the comments!