[Windows] Fix crash on Windows WebView updating the Html Source more than once

src/Controls/samples/Controls.Sample/Pages/Controls/WebViewPage.xaml

@@ -12,6 +12,7 @@
                     Text="HtmlWebViewSource (String)"
                     Style="{StaticResource Headline}"/>
                 <WebView 
+                    x:Name="HtmlSourceWebView"
                     HeightRequest="150"
                     HorizontalOptions="FillAndExpand">
                     <WebView.Source>
@@ -31,6 +32,9 @@
                         </HtmlWebViewSource>
                     </WebView.Source>
                 </WebView>
+                <Button
+                    Text="Update Source"
+                    Clicked="OnUpdateHtmlSourceClicked"/>
                 <Label
                     Text="HtmlWebViewSource (File)"
                     Style="{StaticResource Headline}"/>

src/Controls/samples/Controls.Sample/Pages/Controls/WebViewPage.xaml.cs

@@ -28,6 +28,14 @@ protected override void OnDisappearing()
 			MauiWebView.Navigated -= OnMauiWebViewNavigated;
 		}
 
+		void OnUpdateHtmlSourceClicked(object sender, EventArgs args)
+		{
+			Random rnd = new();
+			HtmlWebViewSource htmlWebViewSource = new();
+			HtmlSourceWebView.Source = htmlWebViewSource;
+			htmlWebViewSource.Html += $"<h1>Updated Content {rnd.Next()}!</h1><br>";
+		}
+
 		void OnGoBackClicked(object sender, EventArgs args)
 		{
 			Debug.WriteLine($"CanGoBack {MauiWebView.CanGoBack}");

src/Core/src/Platform/Windows/MauiWebView.cs

@@ -99,11 +99,16 @@ public async void LoadHtml(string? html, string? baseUrl)
 				NavigateToString(!string.IsNullOrEmpty(htmlWithBaseTag) ? htmlWithBaseTag : html);
 
 				// Free up memory after we're done with _internalWebView
-				_internalWebView = null;
+				if (_internalWebView.IsValid())
+				{
+					_internalWebView.Close();
+					_internalWebView = null;
+				}
 			};
 
 			// Kick off the initial navigation
-			_internalWebView.NavigateToString(html);
+			if (_internalWebView.IsValid())
+				_internalWebView.NavigateToString(html);
 		}
 
 		public async void LoadUrl(string? url)

src/Core/src/Platform/Windows/WebViewExtensions.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Threading.Tasks;
 using Microsoft.UI.Xaml.Controls;
 
 namespace Microsoft.Maui.Platform
@@ -80,5 +79,17 @@ public static void EvaluateJavaScript(this WebView2 webView, EvaluateJavaScriptA
 		{
 			request.RunAndReport(webView.ExecuteScriptAsync(request.Script));
 		}
+
+		internal static bool IsValid(this WebView2 webView)
+		{
+			try
+			{
+				return webView is not null && webView.CoreWebView2 is not null;
+			}
+			catch (Exception ex) when (ex is ObjectDisposedException || ex is InvalidOperationException)
+			{
+				return false;
+			}
+		}
 	}
 }

src/Core/tests/DeviceTests/Handlers/WebView/WebViewHandlerTests.Windows.cs

@@ -1,4 +1,6 @@
-using System.Threading.Tasks;
+using System;
+using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Maui.Controls;
 using Microsoft.Maui.DeviceTests.Stubs;
@@ -9,6 +11,52 @@ namespace Microsoft.Maui.DeviceTests
 {
 	public partial class WebViewHandlerTests
 	{
+		[Theory(DisplayName = "UrlSource Updates Correctly")]
+		[InlineData("<h1>Old Source</h1><br>", "<p>New Source</p>\"")]
+		[InlineData("<p>Old Source</p><br>", "<h1>New Source</h1>\"")]
+		public async Task HtmlSourceUpdatesCorrectly(string oldSource, string newSource)
+		{
+			var pageLoadTimeout = TimeSpan.FromSeconds(2);
+
+			await InvokeOnMainThreadAsync(async () =>
+			{
+				var webView = new WebViewStub()
+				{
+					Width = 100,
+					Height = 100,
+					Source = new HtmlWebViewSourceStub { Html = oldSource }
+				};
+
+				var handler = CreateHandler(webView);
+
+				var platformView = handler.PlatformView;
+
+				// Setup the view to be displayed/parented and run our tests on it
+				await platformView.AttachAndRun(async () =>
+				{
+					// Wait for the page to load
+					var tcsLoaded = new TaskCompletionSource<bool>();
+					var ctsTimeout = new CancellationTokenSource(pageLoadTimeout);
+					ctsTimeout.Token.Register(() => tcsLoaded.TrySetException(new TimeoutException($"Failed to load HTML")));
+
+					webView.NavigatedDelegate = (evnt, url, result) =>
+					{
+						// Set success when we have a successful nav result
+						if (result == WebNavigationResult.Success)
+							tcsLoaded.TrySetResult(result == WebNavigationResult.Success);
+					};
+
+					// Load the new Source
+					webView.Source = new HtmlWebViewSourceStub { Html = newSource };
+
+					handler.UpdateValue(nameof(IWebView.Source));
+
+					// If the new source is loaded without exceptions, the test has passed
+					Assert.True(await tcsLoaded.Task);
+				});
+			});
+		}
+
 		[Fact(DisplayName = "Closing Window With WebView Doesnt Crash")]
 		public async Task ClosingWindowWithWebViewDoesntCrash()
 		{

src/Core/tests/DeviceTests/Stubs/HtmlWebViewSourceStub.cs

@@ -0,0 +1,12 @@
+namespace Microsoft.Maui.DeviceTests.Stubs
+{
+	class HtmlWebViewSourceStub : IWebViewSource
+	{
+		public string Html { get; set; }
+
+		public void Load(IWebViewDelegate webViewDelegate)
+		{
+			webViewDelegate.LoadHtml(Html, null);
+		}
+	}
+}