Fix a couple life cycle scenarios on shell modals

src/Controls/src/Core/Page.cs

@@ -470,7 +470,7 @@ public void SendAppearing()
 			// Visual Hierarchy
 			// The window/application will take care of re-firing this appearing 
 			// if it needs to
-			var window = this.FindParentOfType<Window>();
+			var window = this.FindParentOfType<IWindow>();
 			if (window?.Parent == null)
 			{
 				return;

src/Controls/src/Core/Shell/Shell.cs

@@ -1693,7 +1693,14 @@ protected override async Task OnPushModal(Page modal, bool animated)
 				modal.Parent = (Element)_shell.FindParentOfType<IWindow>();
 
 				if (!_shell.CurrentItem.CurrentItem.IsPushingModalStack)
+				{
+					if (ModalStack.Count > 0)
+					{
+						ModalStack[ModalStack.Count - 1].SendDisappearing();
+					}
+
 					modal.SendAppearing();
+				}
 
 				await base.OnPushModal(modal, animated);
 

src/Controls/src/Core/Shell/ShellSection.cs

@@ -408,6 +408,11 @@ async Task PrepareCurrentStackForBeingReplaced(ShellNavigationRequest request, S
 								continue;
 						}
 
+						// This is the page that we will eventually get to once we've finished
+						// modifying the existing navigation stack
+						// So we want to fire appearing on it						
+						navPage.SendAppearing();
+
 						IsPoppingModalStack = true;
 
 						while (navStack.Count > popCount && Navigation.ModalStack.Count > 0)

src/Controls/tests/Core.UnitTests/ShellLifeCycleTests.cs

@@ -318,7 +318,6 @@ public void AppearingOnShellItemChanged()
 			Assert.False(state.ContentAppearing);
 		}
 
-
 		[Fact]
 		public async Task ShellPartWithModalPush()
 		{
@@ -336,7 +335,6 @@ public async Task ShellPartWithModalPush()
 			lifeCycleState.AllTrue();
 		}
 
-
 		[Fact]
 		public async Task ShellPartWithPagePush()
 		{

src/Controls/tests/Core.UnitTests/ShellModalTests.cs

@@ -12,6 +12,50 @@ namespace Microsoft.Maui.Controls.Core.UnitTests
 
 	public class ShellModalTests : ShellTestBase
 	{
+		[Fact]
+		public async Task AppearingAndDisappearingFireOnMultipleModals()
+		{
+			var windowPage = new ContentPage();
+			var modalPage1 = new ContentPage();
+			var modalPage2 = new ContentPage();
+
+			int modal1Appearing = 0;
+			int modal1Disappearing = 0;
+			int modal2Appearing = 0;
+			int modal2Disappearing = 0;
+			int windowAppearing = 0;
+			int windowDisappearing = 0;
+
+			modalPage1.Appearing += (_, _) => modal1Appearing++;
+			modalPage1.Disappearing += (_, _) => modal1Disappearing++;
+
+			modalPage2.Appearing += (_, _) => modal2Appearing++;
+			modalPage2.Disappearing += (_, _) => modal2Disappearing++;
+
+			windowPage.Appearing += (_, _) => windowAppearing++;
+			windowPage.Disappearing += (_, _) => windowDisappearing++;
+
+			var window = new TestWindow(new TestShell() { CurrentItem = windowPage });
+			await windowPage.Navigation.PushModalAsync(modalPage1);
+			Assert.Equal(1, modal1Appearing);
+
+			await windowPage.Navigation.PushModalAsync(modalPage2);
+			Assert.Equal(1, modal2Appearing);
+			Assert.Equal(1, modal1Disappearing);
+
+			await windowPage.Navigation.PopModalAsync();
+			await windowPage.Navigation.PopModalAsync();
+
+			Assert.Equal(2, modal1Appearing);
+			Assert.Equal(2, modal1Disappearing);
+
+			Assert.Equal(1, modal2Appearing);
+			Assert.Equal(1, modal2Disappearing);
+
+			Assert.Equal(2, windowAppearing);
+			Assert.Equal(1, windowDisappearing);
+		}
+
 		[Fact]
 		public async Task BasicModalBehaviorTest()
 		{