Router incorrectly calls SetParametersAsync multiple times

[Liero]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

WHEN I'm on /index?queryparam=abc and I click a link to /index/999 which is handled by the same component,

THEN SetParametersAsync is called twice:

1. With QueryParam=null
2. With Id=999, QueryParam="abc"

      OnNavigateAsync to 'index?queryparam=abc'
      SetParametersAsync Id:0, QueryParam:abc

      OnNavigateAsync to 'index/999'
      SetParametersAsync Id:0, QueryParam:
      SetParametersAsync Id:999, QueryParam:

This is causing a lot of issue when trying to load data based on parameters.

@page "/index"
@page "/index/{id:int}"
@inject ILogger<Index> _logger

<a href="/index?queryparam=abc">queryparam=def</a>
<a href="/index/999">/999</a>

@code {
    [Parameter] public int Id { get; set; }
    [Parameter, SupplyParameterFromQuery(Name = "queryparam")] public string? QueryParamProperty { get; set; }

    public override async Task SetParametersAsync(ParameterView parameters)
    {
        await base.SetParametersAsync(parameters);
        _logger.LogInformation($"SetParametersAsync Id:{Id}, QueryParam:{QueryParamProperty}");
    }
}

This only happens under specific circumstances:

1. App must have authorization enabled
2. there is OnNavigateAsync handler on the Router
3. there is CascadingAuthenticationState on top of the Router (default in blazor template)

@inject IConfiguration Config
<CascadingAuthenticationState>
<Router AppAssembly="@typeof(Program).Assembly" OnNavigateAsync="OnNavigateAsyncHandler">
    <Found Context="routeData">
        <AuthorizeRouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)">
        </AuthorizeRouteView>
        <FocusOnNavigate RouteData="@routeData" Selector="[data-action=search]" />
    </Found>
    <NotFound>
    </NotFound>

</Router>
</CascadingAuthenticationState>
@code {
    [Inject] NavigationManager NavigationManager { get; set; } = default!;
    [Inject] AuthenticationStateProvider AuthenticationStateProvider { get; set; } = default!;
    [Inject] ILogger<App> Logger { get; set; } = default!;

    
    protected override async Task OnInitializedAsync()
    {
        ClaimsPrincipal user = (await AuthenticationStateProvider.GetAuthenticationStateAsync()).User;
        await Task.Delay(100);

        await base.OnInitializedAsync();
    }

    void OnNavigateAsyncHandler(NavigationContext context)
    {
        Logger.LogInformation("OnNavigateAsync to '{Path}'", context.Path);
    }
}

Expected Behavior

SetParametersAsync should be called only once per single navigation event

Steps To Reproduce

1. Download reproducible demo: https://1drv.ms/u/s!An7wnk66a6RRlrI7ETRR9LsXHi2cmg?e=FsLOC2
2. Start using Visual Studio
3. Register new user (it uses lndividualAccounts authorization)
4. Login
5. Navigate to /index?queryparam=abc
6. Click the /999 link
7. Check the console/debug logs

Exceptions (if any)

No response

.NET Version

6.0.400

Anything else?

.NET SDK (reflecting any global.json):
Version: 6.0.400
Commit: 7771abd614

Runtime Environment:
OS Name: Windows
OS Version: 10.0.22000
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\6.0.400\

global.json file:
Not found

Host:
Version: 6.0.8
Architecture: x64
Commit: 55fb7ef977

Thanks for contacting us.
We're moving this issue to the .NET 8 Planning milestone for future evaluation / consideration. Because it's not immediately obvious that this is a bug in our framework, we would like to keep this around to collect more feedback, which can later help us determine the impact of it. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[TanayParikh]

@Liero, can you please provide the minimal reproduction application as a publicly hosted GitHub repository?

[Liero]

I've added my test project to github: https://github.com/Liero/Bug_Router_Querystring_SetParameters

Please, investigate it.

If I'm right, this is already causing a lot of nasty bugs to many users that have no idea, because it is hard to spot. It wasn't easy to track it down.

[danm-de]

Hello,
we have the same issue in our in-house application (Blazor server-side). The error occurs when we define a <CascadingValue> element with a complex type (custom class) as value. If a child component has a [CascadingParameter] property, the SetParametersAsync method will be called twice for each parameter change:

• The first time with the previous (old) values.
• The second time with the actual values.

This is actually a big problem if you bind properties (marked with [Parameter] or [Parameter, SupplyParameterFromQuery]) to other components. Imagine the following:

1. The user changes a datagrid's page from 2 to 3. A data-bind property called Page is updated to 3. A PageChanged event handler loads new data from a remote source and triggers the NavigationManager to update the browser URI from http://myapp/persons?page=2 to http://myapp/persons?page=3 (Deep linking is still a desired feature - even at SPAs).
2. The query parameter named page requires Blazor to update the property [Parameter,SupplyParameterFromQuery(Name="page")] Page { get; set; }
3. SetParametersAsync is called twice. The first time with the previous value Page=2, the second time with actual value Page=3.
4. Data-binding (property Page) triggers the datagrid to switch back from page 3 to page 2, ....

The problem does not occur when using <CascadingValue ... IsFixed="True"> . Unfortunately, this is not applicable in every situation.

I've made a sample project: https://github.com/danm-de/BlazorSetParametersAsyncBug

In the following picture you can see that the method SetParametersAsync called twice:

[axylophon]

We have the same problem as @Liero.

The OnParameterSetAsync method is called right before navigating away even to another page under these circumstances:

1. there is an OnNavigateAsync handler on the Router
2. there is a CascadingAuthenticationState on top of the Router (default in blazor template)
3. the current page has at least one query parameter set via SupplyParameterFromQuery

[Liero]

@danm-de , @axylophon : upvote the original issue

[afuersch]

Having the same problem as @Liero, @danm-de or @axylophon
E.g. when having query parameters, which are set via SupplyParameterFromQuery attribute the OnParametersSetAsync is called when navigating away to another page.

Is there any info about investigation or planning of a fix?