Скачать или смотреть How to Use TaskCompletionSource for Navigation Confirmation in Blazor Components

Discover how to leverage `TaskCompletionSource` to effectively manage user navigation in Blazor components. Learn to pause execution until user confirmation!
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This video is based on the question https://stackoverflow.com/q/76094763/ asked by the user 'David Thielen' ( https://stackoverflow.com/u/509627/ ) and on the answer https://stackoverflow.com/a/76105876/ provided by the user 'MrC aka Shaun Curtis' ( https://stackoverflow.com/u/13065781/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Handling User Navigation in Blazor Components

When working with Blazor, especially in situations that require user confirmation before navigating away from a page, developers often seek an effective way to manage asynchronous events. This is particularly important when unsaved changes are present on a form. In this guide, we'll address a common problem faced in Blazor applications: how to pause component method execution until a user confirms or denies a navigation attempt.

The Problem

Imagine a scenario where a user has filled out a form but hasn't saved their changes yet. If they decide to navigate to another page, we want to prompt them with a confirmation dialog asking, "Are you sure you want to leave? You might lose unsaved changes."

In the Blazor Server application, the built-in <NavigationLock> component can be used to handle this logic. We can define an OnBeforeInternalNavigation method that reacts to the user's navigation attempt. Inside this method, we need a way to display the confirmation dialog and halt further execution until the user provides an answer.

Key Questions:

Is it appropriate to block execution for user input?

Answer: In this scenario, yes. When handling critical user decisions, it makes sense to halt navigation until the user has made a clear decision.

What's the best way to manage this?

Answer: The TaskCompletionSource class provides a clean way to wait asynchronously for a user’s response.

The Solution

To illustrate how this can be implemented, let’s walk through a code example that utilizes a Bootstrap modal alongside TaskCompletionSource.

Step-by-Step Breakdown

Create the Component Structure:
Begin by setting up the modal that will prompt the user for confirmation.

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

Define User Response Handling:
This involves setting up the TaskCompletionSource to wait for the user's input.

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

Manage User Actions:
Set up methods that respond to button clicks in the dialog:

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

Conclusion

By implementing the TaskCompletionSource pattern along with the Bootstrap modal, you can provide users with a seamless experience that clearly communicates the consequences of their navigation decisions. Users can confidently decide whether to proceed with the navigation or stay on the current page.

In summary, leveraging async programming with TaskCompletionSource allows us to write clean, understandable code while maintaining a responsive user interface in Blazor applications.

Feel free to use this approach in your own Blazor projects whenever a user's decision could impact unsaved data. Happy coding!