Toggling Header/Footer in CollectionView Dynamically throws an except…

…ion (#25743)

* Fixed - 25724 : "ObjectDisposedException" When Toggling Header/Footer in CollectionView Dynamically

* updating nullable enable property

* reverting unnecessary changes

---------

Co-authored-by: praveenkumarkarunanithi <praveenkumar.karunanithi@syncfusion.com>

src/Controls/src/Core/Handlers/Items/iOS/ItemsViewController.cs

@@ -577,7 +577,7 @@ internal void UpdateView(object view, DataTemplate viewTemplate, ref UIView uiVi
 
 				uiView?.Dispose();
 				uiView = null;
-
+				formsElement?.Handler?.DisconnectHandler();
 				formsElement = null;
 			}
 			else

src/Controls/tests/TestCases.HostApp/Issues/Issue25724.xaml

@@ -0,0 +1,51 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="Maui.Controls.Sample.Issues.Issue25724"
+             xmlns:local="clr-namespace:Maui.Controls.Sample.Issues"
+             x:Name="ThisMainPage"
+             Title="Main Page">
+
+  <Grid RowDefinitions="Auto,*">
+
+    <HorizontalStackLayout
+          Grid.Row="0"
+          Padding="20"
+          HorizontalOptions="Center"
+          Spacing="20">
+       <Button AutomationId="ToggleHeaderButton" Text="Toggle Header" Clicked="ToggleHeader"></Button>
+        <Button AutomationId="ToggleFooterButton" Text="Toggle Footer" Clicked="ToggleFooter"></Button>
+    </HorizontalStackLayout>
+
+    <CollectionView x:Name="CollectionView" Grid.Row="1" ItemsSource="{Binding ItemList}">
+
+      <CollectionView.Header>
+          <Label
+              Padding="10"
+              FontAttributes="Bold"
+              FontSize="Large"
+              Text="This Is A Header" />
+      </CollectionView.Header>
+
+      <CollectionView.ItemTemplate>
+        <DataTemplate>
+          <Label Padding="20,5,5,5" Text="{Binding .}" />
+        </DataTemplate>
+      </CollectionView.ItemTemplate>
+
+      <CollectionView.EmptyView>
+          <Label Padding="20,5,5,5" Text="Empty" />
+      </CollectionView.EmptyView>
+
+      <CollectionView.Footer>
+          <Label
+              Padding="10"
+              FontAttributes="Bold"
+              FontSize="Large"
+              Text="This Is A Footer" />
+      </CollectionView.Footer>
+
+    </CollectionView>
+
+  </Grid>
+</ContentPage>

src/Controls/tests/TestCases.HostApp/Issues/Issue25724.xaml.cs

@@ -0,0 +1,54 @@
+#nullable enable
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+using System.Windows.Input;
+
+namespace Maui.Controls.Sample.Issues
+{
+	[XamlCompilation(XamlCompilationOptions.Compile)]
+	[Issue(IssueTracker.Github, 25724, "ObjectDisposedException When Toggling Header/Footer in CollectionView Dynamically", PlatformAffected.iOS)]
+
+	public partial class Issue25724 : ContentPage
+	{
+		object? header;
+		object? footer;
+		public Issue25724()
+		{
+			InitializeComponent();
+			BindingContext = new Issue25724ViewModel();
+		}
+
+		void ToggleHeader(object sender, System.EventArgs e)
+		{
+			header = CollectionView.Header ?? header;
+
+			if (CollectionView.Header == null)
+				CollectionView.Header = header;
+			else
+				CollectionView.Header = null;
+		}
+
+		void ToggleFooter(object sender, System.EventArgs e)
+		{
+			footer = CollectionView.Footer ?? footer;
+
+			if (CollectionView.Footer == null)
+				CollectionView.Footer = footer;
+			else
+				CollectionView.Footer = null;
+		}
+
+		internal class Issue25724ViewModel
+		{
+			public ObservableCollection<string> ItemList { get; set; }
+			public Issue25724ViewModel()
+			{
+				// Initialize the ItemList
+				ItemList = new ObservableCollection<string>();
+			}
+
+		}
+
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue25724.cs

@@ -0,0 +1,25 @@
+#if IOS || MACCATALYST
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	internal class Issue25724 : _IssuesUITest
+	{
+		public Issue25724(TestDevice device) : base(device) { }
+
+		public override string Issue => "ObjectDisposedException When Toggling Header/Footer in CollectionView Dynamically";
+
+		[Test]
+		[Category(UITestCategories.CollectionView)]
+		public void CollectionViewDynamicHeaderShouldNotCrashOnDisplay()
+		{
+			App.WaitForElement("This Is A Header");
+            App.Tap("ToggleHeaderButton"); // This is the button that toggles the header to null
+            App.Tap("ToggleHeaderButton");// This is the button that toggles the header back to the original value
+            App.WaitForElement("This Is A Header");
+		}
+	}
+}
+#endif