Add WebViewManager.TryDispatchAsync() method (#46644)

This enables callers to invoke methods with access to the scoped services used in BlazorWebView controls.

Author: Eilon

src/Components/WebView/WebView/src/PageContext.cs

@@ -25,6 +25,7 @@ internal sealed class PageContext : IAsyncDisposable
     public WebViewNavigationManager NavigationManager { get; }
     public WebViewJSRuntime JSRuntime { get; }
     public WebViewRenderer Renderer { get; }
+    public IServiceProvider ServiceProvider => _serviceScope.ServiceProvider;
 
     public PageContext(
         Dispatcher dispatcher,
@@ -35,17 +36,16 @@ public PageContext(
         string startUrl)
     {
         _serviceScope = serviceScope;
-        var services = serviceScope.ServiceProvider;
 
-        NavigationManager = (WebViewNavigationManager)services.GetRequiredService<NavigationManager>();
+        NavigationManager = (WebViewNavigationManager)ServiceProvider.GetRequiredService<NavigationManager>();
         NavigationManager.AttachToWebView(ipcSender, baseUrl, startUrl);
 
-        JSRuntime = (WebViewJSRuntime)services.GetRequiredService<IJSRuntime>();
+        JSRuntime = (WebViewJSRuntime)ServiceProvider.GetRequiredService<IJSRuntime>();
         JSRuntime.AttachToWebView(ipcSender);
 
-        var loggerFactory = services.GetRequiredService<ILoggerFactory>();
+        var loggerFactory = ServiceProvider.GetRequiredService<ILoggerFactory>();
         var jsComponents = new JSComponentInterop(jsComponentsConfiguration);
-        Renderer = new WebViewRenderer(services, dispatcher, ipcSender, loggerFactory, JSRuntime, jsComponents);
+        Renderer = new WebViewRenderer(ServiceProvider, dispatcher, ipcSender, loggerFactory, JSRuntime, jsComponents);
     }
 
     public async ValueTask DisposeAsync()

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

@@ -1 +1,2 @@
 #nullable enable
+Microsoft.AspNetCore.Components.WebView.WebViewManager.TryDispatchAsync(System.Action<System.IServiceProvider!>! workItem) -> System.Threading.Tasks.Task<bool>!

src/Components/WebView/WebView/src/WebViewManager.cs

@@ -166,6 +166,38 @@ protected void MessageReceived(Uri sourceUri, string message)
         });
     }
 
+    /// <summary>
+    /// Calls the specified <paramref name="workItem"/> asynchronously and passes in the scoped services available to Razor components.
+    /// This method will not throw any exceptions if it is unable to call the specified <paramref name="workItem"/>, but if it does call it, then exceptions may still be thrown by the <paramref name="workItem"/> itself.
+    /// </summary>
+    /// <param name="workItem">The action to call.</param>
+    /// <returns>Returns a <see cref="Task"/> representing <c>true</c> if the <paramref name="workItem"/> was called, or <c>false</c> if it was not called because Blazor is not currently running.</returns>
+    /// <exception cref="ArgumentNullException">Thrown if <paramref name="workItem"/> is <c>null</c>.</exception>
+    public async Task<bool> TryDispatchAsync(Action<IServiceProvider> workItem)
+    {
+        ArgumentNullException.ThrowIfNull(workItem);
+
+        var capturedCurrentPageContext = _currentPageContext;
+
+        if (capturedCurrentPageContext is null)
+        {
+            return false;
+        }
+
+        return await capturedCurrentPageContext.Renderer.Dispatcher.InvokeAsync(() =>
+        {
+            if (capturedCurrentPageContext != _currentPageContext)
+            {
+                // If the captured context doesn't match the current context, that means that there was something like
+                // a navigation event that caused the original page to be detached and a new one attached. Thus, we
+                // cancel out of the operation and return failure.
+                return false;
+            }
+            workItem(_currentPageContext.ServiceProvider);
+            return true;
+        });
+    }
+
     /// <summary>
     /// Tries to provide the response content for a given network request.
     /// </summary>