[Windows] Fix for Grouping collection view without data template results in displaying the default string representation of the object

src/Controls/src/Core/Handlers/Items/GroupableItemsViewHandler.Windows.cs

@@ -1,7 +1,5 @@
 #nullable disable
 using System;
-using System.Collections.Generic;
-using System.Text;
 using Microsoft.Maui.Controls.Platform;
 using Microsoft.Maui.Handlers;
 using Microsoft.UI.Xaml.Controls;
@@ -41,6 +39,19 @@ protected override void UpdateItemTemplate()
 		{
 			base.UpdateItemTemplate();
 
+			// When a GroupFooterTemplate is set but no ItemTemplate, the fake footer item
+			// (GroupFooterItemTemplateContext) appended to each group's Items list needs a
+			// template to render correctly.  Without a selector WinUI calls ToString() on it,
+			// displaying the class name instead of the bound footer content.
+			if (Element.ItemTemplate is null && ItemsView.IsGrouped && ItemsView.GroupFooterTemplate is not null)
+			{
+				ListViewBase.ItemTemplateSelector = new GroupFooterDataTemplateSelector();
+			}
+			else
+			{
+				ListViewBase.ItemTemplateSelector = null;
+			}
+
 			ListViewBase.GroupStyleSelector = new GroupHeaderStyleSelector();
 		}
 	}

src/Controls/src/Core/Platform/Windows/CollectionView/GroupFooterDataTemplateSelector.cs

@@ -0,0 +1,33 @@
+using UWPApp = Microsoft.UI.Xaml.Application;
+using UWPDataTemplate = Microsoft.UI.Xaml.DataTemplate;
+using WinDataTemplateSelector = Microsoft.UI.Xaml.Controls.DataTemplateSelector;
+
+namespace Microsoft.Maui.Controls.Platform;
+
+// Selects ItemsViewDefaultTemplate for fake group-footer items (GroupFooterItemTemplateContext)
+// so that the GroupFooterTemplate is applied when no ItemTemplate is set on the CollectionView.
+// All other items return null, letting WinUI fall back to its default ToString() rendering.
+internal partial class GroupFooterDataTemplateSelector : WinDataTemplateSelector
+{
+	readonly UWPDataTemplate? _footerTemplate;
+
+	public GroupFooterDataTemplateSelector()
+	{
+		_footerTemplate = UWPApp.Current.Resources["ItemsViewDefaultTemplate"] as UWPDataTemplate;
+	}
+
+	protected override UWPDataTemplate SelectTemplateCore(object item)
+	{
+		if (item is GroupFooterItemTemplateContext)
+		{
+			return _footerTemplate!;
+		}
+
+		return null!;
+	}
+
+	protected override UWPDataTemplate SelectTemplateCore(object item, Microsoft.UI.Xaml.DependencyObject container)
+	{
+		return SelectTemplateCore(item);
+	}
+}

src/Controls/src/Core/Platform/Windows/CollectionView/GroupedItemTemplateCollection.cs

@@ -1,6 +1,7 @@
 #nullable disable
 using System;
 using System.Collections;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Collections.Specialized;
 
@@ -67,13 +68,33 @@ public void Dispose()
 		GroupTemplateContext CreateGroupTemplateContext(object group)
 		{
 			var groupHeaderTemplateContext = _groupHeaderTemplate != null
-					? new ItemTemplateContext(_groupHeaderTemplate, group, _container, mauiContext: _mauiContext) : null;
+				? new ItemTemplateContext(_groupHeaderTemplate, group, _container, mauiContext: _mauiContext) : null;
 
 			var groupFooterTemplateContext = _groupFooterTemplate != null
 				? new GroupFooterItemTemplateContext(_groupFooterTemplate, group, _container, mauiContext: _mauiContext) : null;
 
 			// This is where we'll eventually look at GroupItemPropertyName
-			var groupItemsList = TemplatedItemSourceFactory.Create(group as IEnumerable, _itemTemplate, _container, mauiContext: _mauiContext);
+			object groupItemsList;
+			if (_itemTemplate is not null)
+			{
+				groupItemsList = TemplatedItemSourceFactory.Create(group as IEnumerable, _itemTemplate, _container, mauiContext: _mauiContext);
+			}
+			else
+			{
+				// When no ItemTemplate is set, copy the raw group items into a new list so that:
+				// WinUI calls ToString() on the actual data objects (not on ItemTemplateContext wrappers).
+				var rawItems = new List<object>();
+				var groupEnumerable = group as IEnumerable;
+				if (groupEnumerable is not null)
+				{
+					foreach (var item in groupEnumerable)
+					{
+						rawItems.Add(item);
+					}
+				}
+
+				groupItemsList = rawItems;
+			}
 
 			return new GroupTemplateContext(groupHeaderTemplateContext, groupFooterTemplateContext, groupItemsList);
 		}

src/Controls/tests/TestCases.HostApp/Issues/Issue23293.cs

@@ -0,0 +1,73 @@
+namespace Controls.TestCases.HostApp.Issues;
+
+[Issue(IssueTracker.Github, 23293, "Grouping collection view without data template results in displaying the default string representation of the object", PlatformAffected.UWP)]
+public class Issue23293 : ContentPage
+{
+	public List<Issue23293AnimalGroup> Animals { get; set; } = new List<Issue23293AnimalGroup>();
+
+	public Issue23293()
+	{
+		CreateAnimalsCollection();
+
+		CollectionView collectionViewWithoutDataTemplate = new CollectionView
+		{
+			AutomationId = "CollectionViewWithoutDataTemplate",
+			ItemsSource = Animals,
+			IsGrouped = true,
+		};
+
+		CollectionView collectionViewWithGroupTemplates = new CollectionView
+		{
+			AutomationId = "CollectionViewWithGroupTemplates",
+			ItemsSource = Animals,
+			IsGrouped = true,
+			GroupHeaderTemplate = new DataTemplate(() =>
+			{
+				Label label = new Label { FontSize = 14, FontAttributes = FontAttributes.Bold, BackgroundColor = Colors.LightGray };
+				label.SetBinding(Label.TextProperty, "Name");
+				return label;
+			}),
+			GroupFooterTemplate = new DataTemplate(() =>
+			{
+				Label label = new Label { FontSize = 12, BackgroundColor = Colors.LightBlue, AutomationId = "GroupFooterLabel" };
+				label.SetBinding(Label.TextProperty, "Name", stringFormat: "End of {0}");
+				return label;
+			}),
+		};
+
+		Grid grid = new Grid
+		{
+			Padding = 10,
+		};
+
+		grid.RowDefinitions.Add(new RowDefinition { Height = GridLength.Auto });
+		grid.RowDefinitions.Add(new RowDefinition { Height = GridLength.Star });
+		grid.RowDefinitions.Add(new RowDefinition { Height = GridLength.Auto });
+		grid.RowDefinitions.Add(new RowDefinition { Height = GridLength.Star });
+
+		grid.Add(new Label { Text = "No ItemTemplate - items should show animal names", FontSize = 12, FontAttributes = FontAttributes.Bold }, 0, 0);
+		grid.Add(collectionViewWithoutDataTemplate, 0, 1);
+		grid.Add(new Label { Text = "No ItemTemplate with Header/Footer - header shows group name, items show animal name, footer shows 'End of Bears'", FontSize = 12, FontAttributes = FontAttributes.Bold }, 0, 2);
+		grid.Add(collectionViewWithGroupTemplates, 0, 3);
+
+		Content = grid;
+	}
+
+	void CreateAnimalsCollection()
+	{
+		Animals.Add(new Issue23293AnimalGroup("Bears", new List<string>
+		{
+			"American Black Bear",
+		}));
+	}
+}
+
+public class Issue23293AnimalGroup : List<string>
+{
+	public string Name { get; set; }
+
+	public Issue23293AnimalGroup(string name, List<string> animals) : base(animals)
+	{
+		Name = name;
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue23293.cs

@@ -0,0 +1,20 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue23293 : _IssuesUITest
+{
+	public Issue23293(TestDevice device) : base(device) { }
+
+	public override string Issue => "Grouping collection view without data template results in displaying the default string representation of the object";
+
+	[Test]
+	[Category(UITestCategories.CollectionView)]
+	public void GroupedCollectionViewWithoutItemTemplateRendersCorrectly()
+	{
+		App.WaitForElement("GroupFooterLabel");
+		VerifyScreenshot();
+	}
+}