@inject UserDataProvider UserDataProvider
@implements IDisposable

@if (state == null) {
    <p>loading...</p>
} else {
    <CascadingValue Value="@state" IsFixed="false">@ChildContent</CascadingValue>
}

@code{
    private UserData state = null;

    [Parameter]
    public RenderFragment ChildContent { get; set; }

    protected override async Task OnInitializedAsync() {
        UserDataProvider.Changed += UserDataChanged;
        await Refresh();
    }

    public void Dispose() {
        UserDataProvider.Changed -= UserDataChanged;
    }

    private async void UserDataChanged(object sender, EventArgs e) {
        await InvokeAsync(async () => {
            await Refresh();
            StateHasChanged();
        });
    }

    private async Task Refresh() {
        state = await UserDataProvider.Get();
    }
}