NotFound page doesn't get rendered if NavigationManager.NotFound() is called from an async method

[danroth27]

Repro steps:

• Install .NET 10 Preview 6 (10.0.100-preview.6.25321.102)
• Create a default Blazor Web App
• Update Home.razor with:

@page "/"  
@inject NavigationManager NavigationManager

<PageTitle>Home</PageTitle>  

<h1>Hello, world!</h1>  

Welcome to your new app.  


@code {
    [SupplyParameterFromQuery]  
    public string? Id { get; set; }  

    protected override async Task OnInitializedAsync()  
    {
        await Task.Delay(1000);
        if (!string.IsNullOrEmpty(Id))  
        {
            NavigationManager.NotFound();
        }  
    }  
}

• Run the app and browse to /?id=123

Expected result: NotFound page rendered with a 404 status code
Actual result: Home page is rendered with a 404 status code

[ilonatommy]

"default Blazor Web App" - this is an SSR application without global interactivity. We don't have a test case for this yet. It's same issue as we discovered with POST: #62178 (comment) and have to fix.

Basically, the async operation delays the render request and it's added to the next batch. At the same time, triggering NotFound sets the code and stops rendering any further render batches. Re-execution won't kick in because from its perspective, the rendered already handled the request properly. I will add tests to that and try to figure out how to solve it.

[SebastianToet]

Note that all NavigationManager.NavigateTo calls do nothing if called after an asynchronous method call in OnInitializedAsync (in SSR mode):

 protected override async Task OnInitializedAsync()  
 {
        await Task.Delay(1000);
        NavigationManager.NavigateTo("any-route"); //Does nothing
 }  

[ilonatommy]

@SebastianToet, thank you for your report. Could you, please create a separate issue with this problem? It's not connected to the NotFound problem.