fix(ShellView): Fixed an issue in ShellView where items added via c…

…ode would be duplicated (#13326)

Co-authored-by: Mike Corsaro <mikecorsaro@microsoft.com>

src/Controls/src/Core/Handlers/Shell/Windows/ShellView.cs

@@ -155,17 +155,25 @@ IEnumerable<object> IterateItems(List<List<Element>> groups)
 
  foreach (var item in group)
  {
+ bool foundExistingVM = false;
+
  // Check to see if this element already has a VM counter part
  foreach (var navItem in FlyoutItems)
  {
  if (navItem is NavigationViewItemViewModel viewModel && viewModel.Data == item)
+ {
+ foundExistingVM = true;
  yield return viewModel;
+ }
  }
 
- yield return new NavigationViewItemViewModel()
+ if (!foundExistingVM)
  {
- Data = item
- };
+ yield return new NavigationViewItemViewModel()
+ {
+ Data = item
+ };
+ }
  }
  }
  }

src/Controls/tests/DeviceTests/Elements/Shell/ShellTests.Windows.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.Maui.Controls;
@@ -240,6 +241,35 @@ await CreateHandlerAndAddToWindow<ShellHandler>(shell, (handler) =>
  });
  }
 
+ [Fact(DisplayName = "Shell Has Correct Item Count")]
+ public async Task ShellContentHasCorrectItemCount()
+ {
+ SetupBuilder();
+
+ var content1 = new ShellContent();
+ content1.Title = "Hello";
+ content1.Route = $"...";
+
+ var content2 = new ShellContent();
+ content2.Title = "World";
+ content2.Route = $"...";
+
+ var shell = await CreateShellAsync((shell) =>
+ {
+ shell.Items.Add(content1);
+ shell.Items.Add(content2);
+ });
+
+ await CreateHandlerAndAddToWindow<ShellHandler>(shell, (handler) =>
+ {
+ shell.FlyoutBehavior = FlyoutBehavior.Flyout;
+ handler.PlatformView.UpdateMenuItemSource();
+
+ var items = handler.PlatformView.MenuItemsSource as ObservableCollection<object>;
+ Assert.True(items.Count == 2);
+ });
+ }
+
  [Fact(DisplayName = "Single Shell Section with Multiple Children")]
  public async Task SingleShellSectionWithMultipleChildren()
  {