Dispatch forms with streaming rendering

src/Components/Components/src/Binding/CascadingModelBinder.cs

@@ -2,37 +2,48 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Reflection.Metadata;
+using Microsoft.AspNetCore.Components.Binding;
 
-namespace Microsoft.AspNetCore.Components.Binding;
+namespace Microsoft.AspNetCore.Components;
 
-internal class CascadingModelBinder : IComponent
+/// <summary>
+/// Defines the binding context for data bound from external sources.
+/// </summary>
+public class CascadingModelBinder : IComponent
 {
     private RenderHandle _handle;
     private bool _hasRendered;
     private ModelBindingContext? _bindingContext;
 
+    /// <summary>
+    /// The binding context name.
+    /// </summary>
     [Parameter] public string Name { get; set; } = default!;
 
+    /// <summary>
+    /// Specifies the content to be rendered inside this <see cref="CascadingModelBinder"/>.
+    /// </summary>
     [Parameter] public RenderFragment ChildContent { get; set; } = default!;
 
-    public void Attach(RenderHandle renderHandle)
+    void IComponent.Attach(RenderHandle renderHandle)
     {
         _handle = renderHandle;
     }
 
-    public Task SetParametersAsync(ParameterView parameters)
+    Task IComponent.SetParametersAsync(ParameterView parameters)
     {
         if (!_hasRendered)
         {
             _hasRendered = true;
-            _bindingContext = new ModelBindingContext(Name);
             parameters.SetParameterProperties(this);
+
+            _bindingContext = new ModelBindingContext(Name);
             _handle.Render(builder =>
             {
                 builder.OpenComponent<CascadingValue<ModelBindingContext>>(0);
-                builder.AddComponentParameter(1, "IsFixed", true);
-                builder.AddComponentParameter(2, "Value", _bindingContext);
-                builder.AddComponentParameter(3, "ChildContent", ChildContent);
+                builder.AddComponentParameter(1, nameof(CascadingValue<ModelBindingContext>.IsFixed), true);
+                builder.AddComponentParameter(2, nameof(CascadingValue<ModelBindingContext>.Value), _bindingContext);
+                builder.AddComponentParameter(3, nameof(CascadingValue<ModelBindingContext>.ChildContent), ChildContent);
                 builder.CloseComponent();
             });
         }

src/Components/Components/src/Binding/ModelBindingContext.cs

@@ -1,9 +1,26 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
 namespace Microsoft.AspNetCore.Components.Binding;
 
-public class ModelBindingContext(string name)
+/// <summary>
+/// The binding context associated with a given model binding operation.
+/// </summary>
+public class ModelBindingContext
 {
-    public string Name { get; } = name;
+    /// <summary>
+    /// Initializes a new instance of <see cref="ModelBindingContext"/>.
+    /// </summary>
+    /// <param name="name">The context name.</param>
+    public ModelBindingContext(string name)
+    {
+        ArgumentNullException.ThrowIfNull(name);
+
+        Name = name;
+    }
+
+    /// <summary>
+    /// The context name.
+    /// </summary>
+    public string Name { get; }
 }

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

@@ -1,4 +1,13 @@
 #nullable enable
+Microsoft.AspNetCore.Components.Binding.ModelBindingContext
+Microsoft.AspNetCore.Components.Binding.ModelBindingContext.ModelBindingContext(string! name) -> void
+Microsoft.AspNetCore.Components.Binding.ModelBindingContext.Name.get -> string!
+Microsoft.AspNetCore.Components.CascadingModelBinder
+Microsoft.AspNetCore.Components.CascadingModelBinder.CascadingModelBinder() -> void
+Microsoft.AspNetCore.Components.CascadingModelBinder.ChildContent.get -> Microsoft.AspNetCore.Components.RenderFragment!
+Microsoft.AspNetCore.Components.CascadingModelBinder.ChildContent.set -> void
+Microsoft.AspNetCore.Components.CascadingModelBinder.Name.get -> string!
+Microsoft.AspNetCore.Components.CascadingModelBinder.Name.set -> void
 Microsoft.AspNetCore.Components.ComponentBase.DispatchExceptionAsync(System.Exception! exception) -> System.Threading.Tasks.Task!
 Microsoft.AspNetCore.Components.Infrastructure.ComponentStatePersistenceManager.PersistStateAsync(Microsoft.AspNetCore.Components.IPersistentComponentStateStore! store, Microsoft.AspNetCore.Components.Dispatcher! dispatcher) -> System.Threading.Tasks.Task!
 Microsoft.AspNetCore.Components.RenderHandle.DispatchExceptionAsync(System.Exception! exception) -> System.Threading.Tasks.Task!
@@ -41,5 +50,6 @@ override Microsoft.AspNetCore.Components.EventCallback<TValue>.GetHashCode() ->
 override Microsoft.AspNetCore.Components.EventCallback<TValue>.Equals(object? obj) -> bool
 virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.AddPendingTask(Microsoft.AspNetCore.Components.Rendering.ComponentState? componentState, System.Threading.Tasks.Task! task) -> void
 virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.CreateComponentState(int componentId, Microsoft.AspNetCore.Components.IComponent! component, Microsoft.AspNetCore.Components.Rendering.ComponentState? parentComponentState) -> Microsoft.AspNetCore.Components.Rendering.ComponentState!
+virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.DispatchEventAsync(ulong eventHandlerId, Microsoft.AspNetCore.Components.RenderTree.EventFieldInfo? fieldInfo, System.EventArgs! eventArgs, bool quiesce) -> System.Threading.Tasks.Task!
 virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.ShouldTrackNamedEventHandlers() -> bool
 virtual Microsoft.AspNetCore.Components.RenderTree.Renderer.TrackNamedEventId(ulong eventHandlerId, int componentId, string! eventHandlerName) -> void

src/Components/Components/src/RenderTree/Renderer.cs

@@ -372,6 +372,22 @@ protected virtual ComponentState CreateComponentState(int componentId, IComponen
     /// has completed.
     /// </returns>
     public virtual Task DispatchEventAsync(ulong eventHandlerId, EventFieldInfo? fieldInfo, EventArgs eventArgs)
+    {
+        return DispatchEventAsync(eventHandlerId, fieldInfo, eventArgs, quiesce: false);
+    }
+
+    /// <summary>
+    /// Notifies the renderer that an event has occurred.
+    /// </summary>
+    /// <param name="eventHandlerId">The <see cref="RenderTreeFrame.AttributeEventHandlerId"/> value from the original event attribute.</param>
+    /// <param name="eventArgs">Arguments to be passed to the event handler.</param>
+    /// <param name="fieldInfo">Information that the renderer can use to update the state of the existing render tree to match the UI.</param>
+    /// <param name="quiesce">Whether to wait for quiescence or not.</param>
+    /// <returns>
+    /// A <see cref="Task"/> which will complete once all asynchronous processing related to the event
+    /// has completed.
+    /// </returns>
+    public virtual Task DispatchEventAsync(ulong eventHandlerId, EventFieldInfo? fieldInfo, EventArgs eventArgs, bool quiesce)
     {
         Dispatcher.AssertAccess();
 
@@ -402,6 +418,17 @@ public virtual Task DispatchEventAsync(ulong eventHandlerId, EventFieldInfo? fie
             _isBatchInProgress = true;
 
             task = callback.InvokeAsync(eventArgs);
+            if (quiesce)
+            {
+                if (_ongoingQuiescenceTask == null)
+                {
+                    _ongoingQuiescenceTask = task;
+                }
+                else
+                {
+                    AddToPendingTasksWithErrorHandling(task, receiverComponentState);
+                }
+            }
         }
         catch (Exception e)
         {
@@ -417,6 +444,11 @@ public virtual Task DispatchEventAsync(ulong eventHandlerId, EventFieldInfo? fie
             ProcessPendingRender();
         }
 
+        if (quiesce)
+        {
+            return WaitForQuiescence();
+        }
+
         // Task completed synchronously or is still running. We already processed all of the rendering
         // work that was queued so let our error handler deal with it.
         var result = GetErrorHandledTask(task, receiverComponentState);

src/Components/Components/src/RouteView.cs

@@ -3,10 +3,8 @@
 
 #nullable disable warnings
 
-using System;
 using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
-using Microsoft.AspNetCore.Components.Binding;
 using Microsoft.AspNetCore.Components.Rendering;
 using Microsoft.AspNetCore.Components.Routing;
 

src/Components/Endpoints/src/RazorComponentEndpointHost.cs

@@ -39,7 +39,7 @@ private void BuildRenderTree(RenderTreeBuilder builder)
 
         builder.OpenComponent<LayoutView>(0);
         builder.AddComponentParameter(1, nameof(LayoutView.Layout), pageLayoutType);
-        builder.AddComponentParameter(2, nameof(LayoutView.ChildContent), (RenderFragment)RenderPageWithParameters);
+        builder.AddComponentParameter(2, nameof(LayoutView.ChildContent), RenderPageWithParameters);
         builder.CloseComponent();
     }
 

src/Components/Endpoints/src/RazorComponentEndpointInvoker.cs

@@ -4,6 +4,7 @@
 using System.Buffers;
 using System.Text;
 using System.Text.Encodings.Web;
+using Microsoft.AspNetCore.Components.Web.HtmlRendering;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.WebUtilities;
 using Microsoft.Extensions.DependencyInjection;
@@ -32,7 +33,7 @@ private async Task RenderComponentCore()
     {
         _context.Response.ContentType = RazorComponentResultExecutor.DefaultContentType;
 
-        if (await ValidateRequestAsync())
+        if (!await TryValidateRequestAsync(out var isPost))
         {
             // If the request is not valid we've already set the response to a 400 or similar
             // and we can just exit early.
@@ -57,17 +58,19 @@ private async Task RenderComponentCore()
             _context,
             typeof(RazorComponentEndpointHost),
             hostParameters,
-            waitForQuiescence: false);
+            waitForQuiescence: isPost);
+
+        var quiesceTask = isPost ? _renderer.DispatchCapturedEvent() : htmlContent.QuiescenceTask;
 
         // Importantly, we must not yield this thread (which holds exclusive access to the renderer sync context)
         // in between the first call to htmlContent.WriteTo and the point where we start listening for subsequent
         // streaming SSR batches (inside SendStreamingUpdatesAsync). Otherwise some other code might dispatch to the
         // renderer sync context and cause a batch that would get missed.
         htmlContent.WriteTo(writer, HtmlEncoder.Default); // Don't use WriteToAsync, as per the comment above
 
-        if (!htmlContent.QuiescenceTask.IsCompleted)
+        if (!quiesceTask.IsCompleted)
         {
-            await _renderer.SendStreamingUpdatesAsync(_context, htmlContent.QuiescenceTask, writer);
+            await _renderer.SendStreamingUpdatesAsync(_context, quiesceTask, writer);
         }
 
         // Invoke FlushAsync to ensure any buffered content is asynchronously written to the underlying
@@ -76,9 +79,10 @@ private async Task RenderComponentCore()
         await writer.FlushAsync();
     }
 
-    private Task<bool> ValidateRequestAsync()
+    private Task<bool> TryValidateRequestAsync(out bool isPost)
     {
-        if (HttpMethods.IsPost(_context.Request.Method))
+        isPost = HttpMethods.IsPost(_context.Request.Method);
+        if (isPost)
         {
             return Task.FromResult(TrySetFormHandler());
         }

src/Components/Endpoints/src/Rendering/EndpointHtmlRenderer.cs

@@ -119,6 +119,13 @@ protected override void TrackNamedEventId(ulong eventHandlerId, int componentId,
         }
     }
 
+    internal Task DispatchCapturedEvent()
+    {
+        // Clear the list of non-streaming rendering tasks, since we've waited for quiesce before dispatching the event.
+        _nonStreamingPendingTasks.Clear();
+        return DispatchEventAsync(_capturedNamedEvent.EventHandlerId, null, EventArgs.Empty, quiesce: true);
+    }
+
     private static string GenerateComponentPath(ComponentState state)
     {
         // We are generating a path from the root component with te component type names like:

src/Components/Web/src/Forms/EditForm.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Diagnostics;
+using Microsoft.AspNetCore.Components.Binding;
 using Microsoft.AspNetCore.Components.Rendering;
 
 namespace Microsoft.AspNetCore.Components.Forms;
@@ -77,6 +78,11 @@ public EditContext? EditContext
     /// </summary>
     [Parameter] public EventCallback<EditContext> OnInvalidSubmit { get; set; }
 
+    /// <summary>
+    /// Gets the context associated with data bound to the EditContext in this form.
+    /// </summary>
+    [CascadingParameter] public ModelBindingContext? BindingContext { get; set; }
+
     /// <inheritdoc />
     protected override void OnParametersSet()
     {
@@ -122,6 +128,10 @@ protected override void BuildRenderTree(RenderTreeBuilder builder)
         builder.OpenElement(0, "form");
         builder.AddMultipleAttributes(1, AdditionalAttributes);
         builder.AddAttribute(2, "onsubmit", _handleSubmitDelegate);
+        if (BindingContext != null)
+        {
+            builder.SetEventHandlerName(BindingContext.Name);
+        }
         builder.OpenComponent<CascadingValue<EditContext>>(3);
         builder.AddComponentParameter(4, "IsFixed", true);
         builder.AddComponentParameter(5, "Value", _editContext);

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

@@ -1,5 +1,7 @@
 #nullable enable
 *REMOVED*override Microsoft.AspNetCore.Components.Forms.InputFile.OnInitialized() -> void
+Microsoft.AspNetCore.Components.Forms.EditForm.BindingContext.get -> Microsoft.AspNetCore.Components.Binding.ModelBindingContext!
+Microsoft.AspNetCore.Components.Forms.EditForm.BindingContext.set -> void
 Microsoft.AspNetCore.Components.HtmlRendering.Infrastructure.StaticHtmlRenderer
 Microsoft.AspNetCore.Components.HtmlRendering.Infrastructure.StaticHtmlRenderer.BeginRenderingComponent(System.Type! componentType, Microsoft.AspNetCore.Components.ParameterView initialParameters) -> Microsoft.AspNetCore.Components.Web.HtmlRendering.HtmlRootComponent
 Microsoft.AspNetCore.Components.HtmlRendering.Infrastructure.StaticHtmlRenderer.StaticHtmlRenderer(System.IServiceProvider! serviceProvider, Microsoft.Extensions.Logging.ILoggerFactory! loggerFactory) -> void