How to use CascadingValueSource

Question

Has anyone figured out how to interactively use a CascadingValueSource.

The documention shows:

builder.Services.AddCascadingValue(sp =>
{
    var daleks = new Daleks { Units = 789 };
    var source = new CascadingValueSource<Daleks>(daleks, isFixed: false);
    return source;
});

How do you get a reference to the CascadingValueSource to call NotifyChangedAsync?

I'm probably having a senior moment, but you're only in the builder at this point, so you can't get to any services you define.

Answer 1

You can register the cascaded value like so

builder.Services.AddScoped((sp) =>
{
    var daleks = new Daleks { Units = 789 };
    return new CascadingValueSource<Daleks>(daleks, isFixed: false);
});

builder.Services.AddCascadingValue(sp => sp.GetRequiredService<CascadingValueSource<Daleks>>());

With that you can then create a dependency on CascadingValueSource in a component or in a service thats used by a component:

@inject CascadingValueSource<Daleks> source

<button @onclick="OnButtonClick">Notify</button>

@code {
    protected Task OnButtonClick() => source.NotifyChangedAsync();
}

Of course, this example doesn't make much sense. But it shows how you can get the source.