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Root-level cascading values + CascadingAuthenticationState at root (#49204)
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‎src/Components/Authorization/src/CascadingAuthenticationStateServiceCollectionExtensions.cs‎

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// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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using Microsoft.AspNetCore.Components;
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using Microsoft.AspNetCore.Components.Authorization;
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namespace Microsoft.Extensions.DependencyInjection;
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/// <summary>
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/// Extension methods for configuring cascading authentication state on a service collection.
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/// </summary>
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public static class CascadingAuthenticationStateServiceCollectionExtensions
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{
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/// <summary>
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/// Adds cascading authentication state to the <paramref name="serviceCollection"/>. This is equivalent to
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/// having a <see cref="CascadingAuthenticationState"/> component at the root of your component hierarchy.
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/// </summary>
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/// <param name="serviceCollection">The <see cref="IServiceCollection"/>.</param>
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/// <returns>The <see cref="IServiceCollection"/>.</returns>
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public static IServiceCollection AddCascadingAuthenticationState(this IServiceCollection serviceCollection)
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{
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return serviceCollection.AddCascadingValue<Task<AuthenticationState>>(services =>
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{
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var authenticationStateProvider = services.GetRequiredService<AuthenticationStateProvider>();
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return new AuthenticationStateCascadingValueSource(authenticationStateProvider);
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});
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}
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private sealed class AuthenticationStateCascadingValueSource : CascadingValueSource<Task<AuthenticationState>>, IDisposable
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{
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// This is intended to produce identical behavior to having a <CascadingAuthenticationStateProvider>
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// wrapped around the root component.
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private readonly AuthenticationStateProvider _authenticationStateProvider;
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public AuthenticationStateCascadingValueSource(AuthenticationStateProvider authenticationStateProvider)
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: base(authenticationStateProvider.GetAuthenticationStateAsync, isFixed: false)
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{
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_authenticationStateProvider = authenticationStateProvider;
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_authenticationStateProvider.AuthenticationStateChanged += HandleAuthenticationStateChanged;
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}
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private void HandleAuthenticationStateChanged(Task<AuthenticationState> newAuthStateTask)
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{
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// It's OK to discard the task because this only represents the duration of the dispatch to sync context.
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// It handles any exceptions internally by dispatching them to the renderer within the context of whichever
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// component threw when receiving the update. This is the same as how a CascadingValue doesn't get notified
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// about exceptions that happen inside the recipients of value notifications.
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_ = NotifyChangedAsync(newAuthStateTask);
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}
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public void Dispose()
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{
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_authenticationStateProvider.AuthenticationStateChanged -= HandleAuthenticationStateChanged;
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}
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}
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}

‎src/Components/Authorization/src/PublicAPI.Unshipped.txt‎

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#nullable enable
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Microsoft.Extensions.DependencyInjection.CascadingAuthenticationStateServiceCollectionExtensions
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static Microsoft.Extensions.DependencyInjection.CascadingAuthenticationStateServiceCollectionExtensions.AddCascadingAuthenticationState(this Microsoft.Extensions.DependencyInjection.IServiceCollection! serviceCollection) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!

‎src/Components/Components/src/CascadingParameterState.cs‎

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@@ -57,6 +57,7 @@ public static IReadOnlyList<CascadingParameterState> FindCascadingParameters(Com
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private static ICascadingValueSupplier? GetMatchingCascadingValueSupplier(in CascadingParameterInfo info, ComponentState componentState)
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{
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// First scan up through the component hierarchy
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var candidate = componentState;
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do
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{
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candidate = candidate.LogicalParentComponentState;
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} while (candidate != null);
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// We got to the root and found no match, so now look at the providers registered in DI
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foreach (var valueSupplier in componentState.Renderer.ServiceProviderCascadingValueSuppliers)
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{
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if (valueSupplier.CanSupplyValue(info))
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{
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return valueSupplier;
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}
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}
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// No match
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return null;
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}

‎src/Components/Components/src/CascadingValueServiceCollectionExtensions.cs‎

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// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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using Microsoft.AspNetCore.Components;
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namespace Microsoft.Extensions.DependencyInjection;
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/// <summary>
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/// Extension methods for configuring cascading values on an <see cref="IServiceCollection"/>.
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/// </summary>
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public static class CascadingValueServiceCollectionExtensions
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{
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/// <summary>
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/// Adds a cascading value to the <paramref name="serviceCollection"/>. This is equivalent to having
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/// a fixed <see cref="CascadingValue{TValue}"/> at the root of the component hierarchy.
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/// </summary>
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/// <typeparam name="TValue">The value type.</typeparam>
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/// <param name="serviceCollection">The <see cref="IServiceCollection"/>.</param>
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/// <param name="valueFactory">A callback that supplies a fixed value within each service provider scope.</param>
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/// <returns>The <see cref="IServiceCollection"/>.</returns>
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public static IServiceCollection AddCascadingValue<TValue>(
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this IServiceCollection serviceCollection, Func<IServiceProvider, TValue> valueFactory)
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=> serviceCollection.AddScoped<ICascadingValueSupplier>(sp => new CascadingValueSource<TValue>(() => valueFactory(sp), isFixed: true));
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/// <summary>
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/// Adds a cascading value to the <paramref name="serviceCollection"/>. This is equivalent to having
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/// a fixed <see cref="CascadingValue{TValue}"/> at the root of the component hierarchy.
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/// </summary>
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/// <typeparam name="TValue">The value type.</typeparam>
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/// <param name="serviceCollection">The <see cref="IServiceCollection"/>.</param>
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/// <param name="name">A name for the cascading value. If set, <see cref="CascadingParameterAttribute"/> can be configured to match based on this name.</param>
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/// <param name="valueFactory">A callback that supplies a fixed value within each service provider scope.</param>
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/// <returns>The <see cref="IServiceCollection"/>.</returns>
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public static IServiceCollection AddCascadingValue<TValue>(
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this IServiceCollection serviceCollection, string name, Func<IServiceProvider, TValue> valueFactory)
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=> serviceCollection.AddScoped<ICascadingValueSupplier>(sp => new CascadingValueSource<TValue>(name, () => valueFactory(sp), isFixed: true));
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/// <summary>
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/// Adds a cascading value to the <paramref name="serviceCollection"/>. This is equivalent to having
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/// a <see cref="CascadingValue{TValue}"/> at the root of the component hierarchy.
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///
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/// With this overload, you can supply a <see cref="CascadingValueSource{TValue}"/> which allows you
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/// to notify about updates to the value later, causing recipients to re-render. This overload should
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/// only be used if you plan to update the value dynamically.
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/// </summary>
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/// <typeparam name="TValue">The value type.</typeparam>
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/// <param name="serviceCollection">The <see cref="IServiceCollection"/>.</param>
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/// <param name="sourceFactory">A callback that supplies a <see cref="CascadingValueSource{TValue}"/> within each service provider scope.</param>
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/// <returns>The <see cref="IServiceCollection"/>.</returns>
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public static IServiceCollection AddCascadingValue<TValue>(
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this IServiceCollection serviceCollection, Func<IServiceProvider, CascadingValueSource<TValue>> sourceFactory)
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=> serviceCollection.AddScoped<ICascadingValueSupplier>(sourceFactory);
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}

‎src/Components/Components/src/CascadingValueSource.cs‎

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// Licensed to the .NET Foundation under one or more agreements.
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// The .NET Foundation licenses this file to you under the MIT license.
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using System.Collections.Concurrent;
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using Microsoft.AspNetCore.Components.Rendering;
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namespace Microsoft.AspNetCore.Components;
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/// <summary>
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/// Supplies a cascading value that can be received by components using
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/// <see cref="CascadingParameterAttribute"/>.
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/// </summary>
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public class CascadingValueSource<TValue> : ICascadingValueSupplier
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{
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// By *not* making this sealed, people who want to deal with value disposal can subclass this,
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// add IDisposable, and then do what they want during shutdown
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private readonly ConcurrentDictionary<Dispatcher, List<ComponentState>>? _subscribers;
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private readonly bool _isFixed;
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private readonly string? _name;
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// You can either provide an initial value to the constructor, or a func to provide one lazily
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private TValue? _currentValue;
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private Func<TValue>? _initialValueFactory;
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/// <summary>
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/// Constructs an instance of <see cref="CascadingValueSource{TValue}"/>.
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/// </summary>
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/// <param name="value">The initial value.</param>
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/// <param name="isFixed">A flag to indicate whether the value is fixed. If false, all receipients will subscribe for update notifications, which you can issue by calling <see cref="NotifyChangedAsync()"/>. These subscriptions come at a performance cost, so if the value will not change, set <paramref name="isFixed"/> to true.</param>
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public CascadingValueSource(TValue value, bool isFixed) : this(isFixed)
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{
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_currentValue = value;
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}
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/// <summary>
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/// Constructs an instance of <see cref="CascadingValueSource{TValue}"/>.
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/// </summary>
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/// <param name="name">A name for the cascading value. If set, <see cref="CascadingParameterAttribute"/> can be configured to match based on this name.</param>
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/// <param name="value">The initial value.</param>
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/// <param name="isFixed">A flag to indicate whether the value is fixed. If false, all receipients will subscribe for update notifications, which you can issue by calling <see cref="NotifyChangedAsync()"/>. These subscriptions come at a performance cost, so if the value will not change, set <paramref name="isFixed"/> to true.</param>
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public CascadingValueSource(string name, TValue value, bool isFixed) : this(value, isFixed)
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{
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ArgumentNullException.ThrowIfNull(name);
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_name = name;
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}
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/// <summary>
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/// Constructs an instance of <see cref="CascadingValueSource{TValue}"/>.
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/// </summary>
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/// <param name="valueFactory">A callback that produces the initial value when first required.</param>
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/// <param name="isFixed">A flag to indicate whether the value is fixed. If false, all receipients will subscribe for update notifications, which you can issue by calling <see cref="NotifyChangedAsync()"/>. These subscriptions come at a performance cost, so if the value will not change, set <paramref name="isFixed"/> to true.</param>
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public CascadingValueSource(Func<TValue> valueFactory, bool isFixed) : this(isFixed)
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{
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_initialValueFactory = valueFactory;
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}
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/// <summary>
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/// Constructs an instance of <see cref="CascadingValueSource{TValue}"/>.
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/// </summary>
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/// <param name="name">A name for the cascading value. If set, <see cref="CascadingParameterAttribute"/> can be configured to match based on this name.</param>
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/// <param name="valueFactory">A callback that produces the initial value when first required.</param>
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/// <param name="isFixed">A flag to indicate whether the value is fixed. If false, all receipients will subscribe for update notifications, which you can issue by calling <see cref="NotifyChangedAsync()"/>. These subscriptions come at a performance cost, so if the value will not change, set <paramref name="isFixed"/> to true.</param>
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public CascadingValueSource(string name, Func<TValue> valueFactory, bool isFixed) : this(valueFactory, isFixed)
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{
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ArgumentNullException.ThrowIfNull(name);
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_name = name;
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}
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private CascadingValueSource(bool isFixed)
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{
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_isFixed = isFixed;
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if (!_isFixed)
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{
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_subscribers = new();
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}
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}
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/// <summary>
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/// Notifies subscribers that the value has changed (for example, if it has been mutated).
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/// </summary>
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/// <returns>A <see cref="Task"/> that completes when the notifications have been issued.</returns>
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public Task NotifyChangedAsync()
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{
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if (_isFixed)
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{
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throw new InvalidOperationException($"Cannot notify about changes because the {GetType()} is configured as fixed.");
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}
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if (_subscribers?.Count > 0)
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{
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var tasks = new List<Task>();
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foreach (var (dispatcher, subscribers) in _subscribers)
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{
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tasks.Add(dispatcher.InvokeAsync(() =>
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{
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foreach (var subscriber in subscribers)
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{
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subscriber.NotifyCascadingValueChanged(ParameterViewLifetime.Unbound);
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}
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}));
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}
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return Task.WhenAll(tasks);
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}
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else
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{
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return Task.CompletedTask;
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}
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}
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/// <summary>
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/// Notifies subscribers that the value has changed, supplying a new value.
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/// </summary>
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/// <param name="newValue"></param>
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/// <returns>A <see cref="Task"/> that completes when the notifications have been issued.</returns>
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public Task NotifyChangedAsync(TValue newValue)
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{
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_currentValue = newValue;
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_initialValueFactory = null; // This definitely won't be used now
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return NotifyChangedAsync();
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}
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bool ICascadingValueSupplier.IsFixed => _isFixed;
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bool ICascadingValueSupplier.CanSupplyValue(in CascadingParameterInfo parameterInfo)
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{
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if (parameterInfo.Attribute is not CascadingParameterAttribute cascadingParameterAttribute || !parameterInfo.PropertyType.IsAssignableFrom(typeof(TValue)))
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{
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return false;
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}
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// We only consider explicitly requested names, not the property name.
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var requestedName = cascadingParameterAttribute.Name;
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return (requestedName == null && _name == null) // Match on type alone
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|| string.Equals(requestedName, _name, StringComparison.OrdinalIgnoreCase); // Also match on name
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}
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object? ICascadingValueSupplier.GetCurrentValue(in CascadingParameterInfo parameterInfo)
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{
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if (_initialValueFactory is not null)
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{
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_currentValue = _initialValueFactory();
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_initialValueFactory = null;
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}
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return _currentValue;
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}
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void ICascadingValueSupplier.Subscribe(ComponentState subscriber, in CascadingParameterInfo parameterInfo)
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{
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Dispatcher dispatcher = subscriber.Renderer.Dispatcher;
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dispatcher.AssertAccess();
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// The .Add is threadsafe because we are in the sync context for this dispatcher
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_subscribers?.GetOrAdd(dispatcher, _ => new()).Add(subscriber);
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}
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void ICascadingValueSupplier.Unsubscribe(ComponentState subscriber, in CascadingParameterInfo parameterInfo)
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{
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Dispatcher dispatcher = subscriber.Renderer.Dispatcher;
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dispatcher.AssertAccess();
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if (_subscribers?.TryGetValue(dispatcher, out var subscribersForDispatcher) == true)
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{
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// Threadsafe because we're in the sync context for this dispatcher
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subscribersForDispatcher.Remove(subscriber);
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if (subscribersForDispatcher.Count == 0)
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{
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_subscribers.Remove(dispatcher, out _);
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}
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}
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}
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}

‎src/Components/Components/src/PublicAPI.Unshipped.txt‎

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@@ -46,6 +46,13 @@ Microsoft.AspNetCore.Components.CascadingParameterInfo.Attribute.get -> Microsof
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Microsoft.AspNetCore.Components.CascadingParameterInfo.CascadingParameterInfo() -> void
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Microsoft.AspNetCore.Components.CascadingParameterInfo.PropertyName.get -> string!
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Microsoft.AspNetCore.Components.CascadingParameterInfo.PropertyType.get -> System.Type!
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Microsoft.AspNetCore.Components.CascadingValueSource<TValue>
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Microsoft.AspNetCore.Components.CascadingValueSource<TValue>.CascadingValueSource(string! name, System.Func<TValue>! valueFactory, bool isFixed) -> void
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Microsoft.AspNetCore.Components.CascadingValueSource<TValue>.CascadingValueSource(string! name, TValue value, bool isFixed) -> void
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Microsoft.AspNetCore.Components.CascadingValueSource<TValue>.CascadingValueSource(System.Func<TValue>! valueFactory, bool isFixed) -> void
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Microsoft.AspNetCore.Components.CascadingValueSource<TValue>.CascadingValueSource(TValue value, bool isFixed) -> void
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Microsoft.AspNetCore.Components.CascadingValueSource<TValue>.NotifyChangedAsync() -> System.Threading.Tasks.Task!
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Microsoft.AspNetCore.Components.CascadingValueSource<TValue>.NotifyChangedAsync(TValue newValue) -> System.Threading.Tasks.Task!
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Microsoft.AspNetCore.Components.ComponentBase.DispatchExceptionAsync(System.Exception! exception) -> System.Threading.Tasks.Task!
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Microsoft.AspNetCore.Components.IComponentRenderMode
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Microsoft.AspNetCore.Components.Infrastructure.ComponentStatePersistenceManager.PersistStateAsync(Microsoft.AspNetCore.Components.IPersistentComponentStateStore! store, Microsoft.AspNetCore.Components.Dispatcher! dispatcher) -> System.Threading.Tasks.Task!
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Microsoft.AspNetCore.Components.StreamRenderingAttribute.StreamRenderingAttribute(bool enabled) -> void
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*REMOVED*Microsoft.AspNetCore.Components.CascadingParameterAttribute.Name.get -> string?
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*REMOVED*Microsoft.AspNetCore.Components.CascadingParameterAttribute.Name.set -> void
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Microsoft.Extensions.DependencyInjection.CascadingValueServiceCollectionExtensions
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override Microsoft.AspNetCore.Components.CascadingParameterAttribute.Name.get -> string?
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override Microsoft.AspNetCore.Components.CascadingParameterAttribute.Name.set -> void
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override Microsoft.AspNetCore.Components.EventCallback.GetHashCode() -> int
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*REMOVED*Microsoft.AspNetCore.Components.SupplyParameterFromQueryAttribute.Name.set -> void
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override Microsoft.AspNetCore.Components.SupplyParameterFromQueryAttribute.Name.get -> string?
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override Microsoft.AspNetCore.Components.SupplyParameterFromQueryAttribute.Name.set -> void
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static Microsoft.Extensions.DependencyInjection.CascadingValueServiceCollectionExtensions.AddCascadingValue<TValue>(this Microsoft.Extensions.DependencyInjection.IServiceCollection! serviceCollection, string! name, System.Func<System.IServiceProvider!, TValue>! valueFactory) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!
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static Microsoft.Extensions.DependencyInjection.CascadingValueServiceCollectionExtensions.AddCascadingValue<TValue>(this Microsoft.Extensions.DependencyInjection.IServiceCollection! serviceCollection, System.Func<System.IServiceProvider!, Microsoft.AspNetCore.Components.CascadingValueSource<TValue>!>! sourceFactory) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!
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static Microsoft.Extensions.DependencyInjection.CascadingValueServiceCollectionExtensions.AddCascadingValue<TValue>(this Microsoft.Extensions.DependencyInjection.IServiceCollection! serviceCollection, System.Func<System.IServiceProvider!, TValue>! valueFactory) -> Microsoft.Extensions.DependencyInjection.IServiceCollection!
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virtual Microsoft.AspNetCore.Components.Binding.CascadingModelBindingProvider.Subscribe(Microsoft.AspNetCore.Components.Rendering.ComponentState! subscriber) -> void
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virtual Microsoft.AspNetCore.Components.Binding.CascadingModelBindingProvider.Unsubscribe(Microsoft.AspNetCore.Components.Rendering.ComponentState! subscriber) -> void
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virtual Microsoft.AspNetCore.Components.Rendering.ComponentState.DisposeAsync() -> System.Threading.Tasks.ValueTask

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