Fix Shell Navigating event not firing on ShellContent change

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

@@ -1019,6 +1019,24 @@ static void OnCurrentItemChanged(BindableObject bindable, object oldValue, objec
 		{
 			var shellSection = (ShellSection)bindable;
 
+			var isFromHandler =
+				shellSection.GetContext(CurrentItemProperty)?.Values.GetSpecificity() == SetterSpecificity.FromHandler;
+
+			if (!isFromHandler &&
+				newValue is ShellContent newContent &&
+				shellSection.Parent?.Parent is Shell parentShell &&
+				shellSection.IsVisibleSection)
+			{
+				parentShell.NavigationManager.ProposeNavigationOutsideGotoAsync(
+					ShellNavigationSource.ShellContentChanged,
+					parentShell.CurrentItem,
+					shellSection,
+					newContent,
+					shellSection.Stack,
+					canCancel: false,
+					isAnimated: true);
+			}
+
 			if (oldValue is ShellContent oldShellItem)
 				oldShellItem.SendDisappearing();
 
@@ -1028,9 +1046,7 @@ static void OnCurrentItemChanged(BindableObject bindable, object oldValue, objec
 			shellSection.PresentedPageAppearing();
 
 			if (shellSection.Parent?.Parent is IShellController shell && shellSection.IsVisibleSection)
-			{
 				shell.UpdateCurrentState(ShellNavigationSource.ShellContentChanged);
-			}
 
 			shellSection.SendStructureChanged();
 

src/Controls/tests/TestCases.HostApp/Issues/Issue34318.cs

@@ -0,0 +1,117 @@
+using Microsoft.Maui.ApplicationModel;
+using Microsoft.Maui.Controls;
+using Microsoft.Maui.Controls.CustomAttributes;
+
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 34318, "Shell Navigating event should fire on ShellContent change", PlatformAffected.All)]
+public class Issue34318 : Shell
+{
+	Label labelA;
+	Label labelB;
+	Label navigatingCountLabel;
+	int navigatingCount;
+
+	public Issue34318()
+	{
+		labelA = new Label
+		{
+			Text = "Waiting",
+			AutomationId = "ResultLabelA"
+		};
+
+		labelB = new Label
+		{
+			Text = "Waiting",
+			AutomationId = "ResultLabelB"
+		};
+
+		navigatingCountLabel = new Label
+		{
+			Text = "0",
+			AutomationId = "NavigatingCountLabel"
+		};
+
+		var section = new ShellSection();
+
+		var pageA = new Issue34318_PageA(labelA);
+
+		var contentA = new ShellContent
+		{
+			Content = pageA
+		};
+
+		var contentB = new ShellContent
+		{
+			Content = new ContentPage
+			{
+				Title = "PageB",
+				Content = new VerticalStackLayout
+				{
+					Children =
+					{
+						new Label
+						{
+							Text = "Page B",
+							AutomationId = "PageBLabel"
+						},
+						labelB,
+						navigatingCountLabel
+					}
+				}
+			}
+		};
+
+		section.Items.Add(contentA);
+		section.Items.Add(contentB);
+
+		var item = new ShellItem();
+		item.Items.Add(section);
+
+		Items.Add(item);
+
+		Navigating += (_, __) =>
+		{
+			MainThread.BeginInvokeOnMainThread(() =>
+			{
+				navigatingCount++;
+
+				labelA.Text = "Navigating";
+				labelB.Text = "Navigating";
+				navigatingCountLabel.Text = navigatingCount.ToString();
+			});
+		};
+	}
+
+	public class Issue34318_PageA : ContentPage
+	{
+		public Issue34318_PageA(Label label)
+		{
+			Title = "PageA";
+
+			var button = new Button
+			{
+				Text = "Change Content",
+				AutomationId = "ChangeContentButton"
+			};
+
+			button.Clicked += (s, e) =>
+			{
+				Element parent = this;
+
+				while (parent != null && parent is not ShellSection)
+					parent = parent.Parent;
+
+				if (parent is ShellSection section && section.Items.Count > 1)
+				{
+					section.CurrentItem = section.Items[1];
+				}
+			};
+
+			Content = new VerticalStackLayout
+			{
+				Children = { button, label }
+			};
+		}
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue34318.cs

@@ -0,0 +1,37 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue34318 : _IssuesUITest
+{
+	public Issue34318(TestDevice device) : base(device) { }
+
+	public override string Issue => "Shell Navigating event should fire on ShellContent change";
+
+	[Test]
+	[Category(UITestCategories.Shell)]
+	public void NavigatingFiresWhenShellContentChanges()
+	{
+		App.WaitForElement("ChangeContentButton");
+
+		App.WaitForElement("ResultLabelA");
+
+		var initialText = App.FindElement("ResultLabelA").GetText() ?? string.Empty;
+		Assert.That(initialText, Is.EqualTo("Waiting"));
+
+		App.Tap("ChangeContentButton");
+
+		App.WaitForElement("PageBLabel");
+
+		var result = App.WaitForTextToBePresentInElement("ResultLabelB", "Navigating");
+
+		Assert.That(result, Is.True, "Navigating event should have fired and updated the label text");
+
+		var countText = App.FindElement("NavigatingCountLabel").GetText() ?? string.Empty;
+
+		Assert.That(countText, Is.EqualTo("1"),
+			"Navigating event should fire exactly once, not multiple times");
+	}
+}