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jfversluisjfversluis
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Prevent CollectionView.EmptyView from showing up while it shouldn't on iOS (#15122)
* Add repro + fix * Fix build + Add Item Remove button * Tidy up
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‎Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Controls/MyCollectionView.xaml

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<?xml version="1.0" encoding="UTF-8" ?>
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<!-- Used in Issue13794 -->
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<CollectionView
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xmlns="http://xamarin.com/schemas/2014/forms"
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xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
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x:Class="Xamarin.Forms.Controls.Issues.MyCollectionView"
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ItemsSource="{Binding Data}"
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SelectionMode="Single"
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SelectionChanged="CollectionView_SelectionChanged"
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AutomationId="TehCollectionView">
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<CollectionView.EmptyView>
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<Label Text="The collection is empty" BackgroundColor="Transparent" VerticalOptions="CenterAndExpand" HorizontalOptions="FillAndExpand" HorizontalTextAlignment="Center" VerticalTextAlignment="Center" AutomationId="CollectionViewEmptyView" />
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</CollectionView.EmptyView>
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<CollectionView.ItemTemplate>
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<DataTemplate>
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<SwipeView>
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<SwipeView.RightItems>
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<SwipeItems>
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<SwipeItem Text="Delete" BackgroundColor="Red" Invoked="DeleteItem_Invoked" />
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</SwipeItems>
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</SwipeView.RightItems>
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<Label Text="{Binding .}" Padding="20" />
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</SwipeView>
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</DataTemplate>
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</CollectionView.ItemTemplate>
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</CollectionView>

‎Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Controls/MyCollectionView.xaml.cs

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using System;
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using System.Collections.ObjectModel;
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using System.Linq;
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using Xamarin.Forms;
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namespace Xamarin.Forms.Controls.Issues
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{
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public partial class MyCollectionView : CollectionView
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{
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public ObservableCollection<string> Data { get; private set; }
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public MyCollectionView(ObservableCollection<string> data)
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{
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#if APP
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InitializeComponent();
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#endif
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BindingContext = this;
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// Moving this above InitializeComponent fixes the problem.
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Data = data;
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}
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void CollectionView_SelectionChanged(object sender, SelectionChangedEventArgs e)
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{
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if (e.CurrentSelection == null || e.CurrentSelection.Count == 0)
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{
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return;
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}
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SelectedItem = null;
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if (e.CurrentSelection.FirstOrDefault() is String data)
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{
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Console.WriteLine($"Selected: {data}");
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}
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}
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void DeleteItem_Invoked(System.Object sender, System.EventArgs e)
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{
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if (sender is SwipeItem swipeItem && swipeItem.BindingContext is String dataItem)
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{
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Data.Remove(dataItem);
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}
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}
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}
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}

‎Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue13794.cs

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using System;
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using System.Collections.Generic;
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using System.Collections.ObjectModel;
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using Xamarin.Forms.CustomAttributes;
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using Xamarin.Forms.Internals;
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#if UITEST
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using NUnit.Framework;
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using Xamarin.Forms.Core.UITests;
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#endif
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namespace Xamarin.Forms.Controls.Issues
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{
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#if UITEST
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[NUnit.Framework.Category(UITestCategories.CollectionView)]
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#endif
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[Preserve(AllMembers = true)]
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[Issue(IssueTracker.Github, 13794, "[Bug] CollectionView iOS draws both EmptyView and Items/ItemTemplate", PlatformAffected.iOS)]
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public class Issue13794 : TestContentPage
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{
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ObservableCollection<string> _data;
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MyCollectionView _myCollectionView;
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public Issue13794()
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{
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ToolbarItems.Add(new ToolbarItem("Remove item", null, () => { if (_myCollectionView.Data.Count >= 1) _myCollectionView.Data.RemoveAt(0); }));
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var carouselView = new CarouselView()
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{
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IsSwipeEnabled = false
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};
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BindingContext = this;
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// This is gross, but the idea is the page contains the data and passes a refernece to the view.
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// Data is loaded from the page (eg via web request, loaded from file)
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_data = new ObservableCollection<string>();
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_myCollectionView = new MyCollectionView(_data);
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// In my code I was replacing the Footer already defined in the xaml.
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// This didn't seem to contribute to the issue.
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//_myCollectionView.Footer = new BoxView();
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// Add collection view to a CarouselView. This was the only way I could replicate the issue.
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// In my actual app I have 3 different user feeds, and user can change between them.
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carouselView.ItemsSource = new List<View>()
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{
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_myCollectionView,
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};
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// This makes more sense when there is 3 differnet things to select.
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carouselView.ItemTemplate = new MyDataTemplateSelector()
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{
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MyCollectionViewDataTemplate = new DataTemplate(() => _myCollectionView),
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};
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// I was trying to set _myCollectionView as root Content but it doesn't appear to
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// cause the problem. Its related to the CarouselView
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//Content = _myCollectionView;
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// Add data
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var rand = new Random();
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_data.Add(rand.Next().ToString());
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_data.Add(rand.Next().ToString());
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_data.Add(rand.Next().ToString());
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// Does not have the issue if the data is loaded with a delay.
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/*
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Task.Run(async () =>
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{
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await Task.Delay(1000);
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var rand = new Random();
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_data.Add(rand.Next().ToString());
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_data.Add(rand.Next().ToString());
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_data.Add(rand.Next().ToString());
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});
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*/
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var stackLayout = new StackLayout()
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{
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Children =
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{
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new Label()
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{
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Text = "If you don't see the EmptyView and CollectionView items together the test passed",
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Padding = 12,
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BackgroundColor = Color.Black,
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TextColor = Color.White,
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AutomationId = "Instructions"
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},
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carouselView
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}
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};
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Content = stackLayout;
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}
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protected override void Init()
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{
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}
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#if UITEST
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[Test]
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public void EmptyViewAndItemsNotShownTogether()
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{
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// Wait until the collection view is shown
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RunningApp.WaitForElement("TehCollectionView");
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RunningApp.Screenshot("CollectionView should be shown with items and no EmptyView");
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// Verify that the empty view is not shown
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RunningApp.WaitForNoElement("CollectionViewEmptyView");
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}
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#endif
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}
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public class MyDataTemplateSelector : DataTemplateSelector
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{
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public DataTemplate MyCollectionViewDataTemplate { get; set; }
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protected override DataTemplate OnSelectTemplate(object item, BindableObject container)
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{
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if (item is MyCollectionView)
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{
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return MyCollectionViewDataTemplate;
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}
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return null;
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}
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}
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}
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‎Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

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<Compile Include="$(MSBuildThisFileDirectory)Issue14805.cs" />
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<Compile Include="$(MSBuildThisFileDirectory)Issue11954.cs" />
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<Compile Include="$(MSBuildThisFileDirectory)Issue13918.xaml.cs" />
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<Compile Include="$(MSBuildThisFileDirectory)Issue13794.cs" />
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<Compile Include="$(MSBuildThisFileDirectory)Controls\MyCollectionView.xaml.cs">
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<DependentUpon>MyCollectionView.xaml</DependentUpon>
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<SubType>Code</SubType>
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</Compile>
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</ItemGroup>
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<ItemGroup>
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<EmbeddedResource Include="$(MSBuildThisFileDirectory)Bugzilla22229.xaml">
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<EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue13918.xaml">
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<Generator>MSBuild:UpdateDesignTimeXaml</Generator>
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</EmbeddedResource>
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<EmbeddedResource Include="$(MSBuildThisFileDirectory)Controls\MyCollectionView.xaml">
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<SubType>Designer</SubType>
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<Generator>MSBuild:UpdateDesignTimeXaml</Generator>
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</EmbeddedResource>
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</ItemGroup>
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<ItemGroup>
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<EmbeddedResource Include="$(MSBuildThisFileDirectory)Bugzilla27417Xaml.xaml">
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<ItemGroup>
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<EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue14801.xaml">
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<SubType>Designer</SubType>
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<Generator>MSBuild:Compile</Generator>
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<Generator>MSBuild:UpdateDesignTimeXaml</Generator>
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</EmbeddedResource>
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<EmbeddedResource Include="$(MSBuildThisFileDirectory)Issue8804.xaml">
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<SubType>Designer</SubType>

‎Xamarin.Forms.Platform.iOS/CollectionView/ItemsViewController.cs

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public TItemsView ItemsView { get; }
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protected ItemsViewLayout ItemsViewLayout { get; set; }
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bool _initialized;
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bool _isEmpty;
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bool _isEmpty = true;
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bool _emptyViewDisplayed;
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bool _disposed;
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