Скачать или смотреть How to Ensure Smooth Navigation in Your Blazor WebAssembly App: Avoiding the Loader Issue

Discover solutions to manage navigation delays in Blazor WebAssembly applications and enhance user experience by integrating loading components effectively.
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Navigating Smoothly in Your Blazor WebAssembly App: Solving the Loader Display Issue

Blazor WebAssembly offers an exciting way to build interactive web applications, but sometimes developers face tricky navigation issues, particularly when transitioning between pages. One common scenario arises when navigating from an edit page back to a list page. Many users have experienced a situation where a loader component fails to appear during the transition, making it seem as though the application has frozen. This guide explores this problem and offers practical solutions to ensure users always see the loader while their content loads.

The Problem: Missing Loader Component During Navigation

Imagine you have a Blazor WebAssembly app that consists of an Edit page for entities and a List page displaying those entities. When a user updates an entity and saves their changes, the app is expected to display a loading indicator (such as a loader component) while transitioning back to the List page. However, some developers find that the loader doesn't show, leaving users with the impression that the application is unresponsive.

This occurs because the List page's loading logic doesn't break free from the UI thread effectively, resulting in everything operating synchronously. Thus, the new page doesn't get the chance to show the loader component before rendering.

Solution: Implementing Loader Display Strategies

To overcome this issue, there are two effective methods to ensure that the loader component is displayed during your app's navigation transition. Let’s take a closer look at each method.

Method 1: Using OnInitializedAsync to Load the List

The first approach involves leveraging the OnInitializedAsync lifecycle method. This method is called when the component is initialized, making it an ideal time to load your data. Here’s a step-by-step breakdown:

Introduce a Delay to Free the UI Thread: Start by introducing a brief delay to allow the UI thread to build a task continuation. You can achieve this using Task.Delay();.

Load the Data from the Service: After the delay, proceed to populate your list.

Update the UI as Needed: After populating the list, synchronize back to the UI thread.

Here’s what the code might look like:

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

Method 2: Utilizing OnAfterRenderAsync for Data Loading

An alternative approach is to use the OnAfterRenderAsync lifecycle method. Here’s how this method works:

Set the Initial UI State to Loading: When the component first renders, display the loading component by default.

Load the Data during the First Render: Once the component is ready, populate your list asynchronously.

Update the UI Once Data is Loaded: Switch the UI to display the list once the data is successfully retrieved.

Here’s an example of how you can implement this method:

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

Which Method to Choose?

Both methods will help you solve the loader visibility issue, but many developers prefer Method 2 (using OnAfterRenderAsync). This method allows for easy representation of a loading state and can support loading different sections of the UI in parallel, enhancing the overall user experience.

Additionally, remember that in Blazor Server, OnInitializedAsync can be called more than once, while OnAfterRenderAsync will generally only be called once, minimizing unnecessary re-rendering.

A Note on Navigation Manager

Lastly, consider utilizing the NavigationManager.NavigateTo() method, which has an optional second parameter for forced reloading. By providing true as an argument, you can enforce a full refresh of the page, which can be beneficial in certain scenarios, like complex form resets. Experimenting