Some adjustments for all day items control. Removed the leaking part.

Wino.Calendar.ViewModels/Data/CalendarItemViewModel.cs

@@ -24,6 +24,10 @@ namespace Wino.Calendar.ViewModels.Data
 
         public ITimePeriod Period => CalendarItem.Period;
 
+        public bool IsAllDayEvent => ((ICalendarItem)CalendarItem).IsAllDayEvent;
+
+        public bool IsMultiDayEvent => ((ICalendarItem)CalendarItem).IsMultiDayEvent;
+
         public CalendarItemViewModel(CalendarItem calendarItem)
         {
             CalendarItem = calendarItem;

Wino.Calendar/Controls/AllDayItemsControl.xaml

@@ -4,19 +4,20 @@
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:controls="using:Wino.Calendar.Controls"
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:data="using:Wino.Calendar.ViewModels.Data"
     xmlns:domain="using:Wino.Core.Domain"
+    xmlns:helpers="using:Wino.Helpers"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     d:DesignHeight="300"
     d:DesignWidth="400"
     mc:Ignorable="d">
 
     <Grid>
-        <ScrollViewer x:Name="PART_AllDayItemsListScrollHost">
+        <controls:CalendarItemControl
-            <ItemsControl
+            x:Name="SingleAllDayEventHolder"
-                x:Name="PART_AllDayItemsList"
+            CalendarItem="{x:Bind helpers:XamlHelpers.GetFirstAllDayEvent(EventCollection), Mode=OneWay}"
-                ItemTemplate="{x:Bind AllDayEventTemplate}"
+            Visibility="{x:Bind helpers:XamlHelpers.CountToVisibilityConverter(EventCollection.AllDayEvents.Count), Mode=OneWay}" />
-                ItemsSource="{x:Bind EventCollection.AllDayEvents}" />
+
-        </ScrollViewer>
         <Button
             x:Name="AllDayItemsSummaryButton"
             HorizontalAlignment="Stretch"
@@ -36,8 +37,7 @@
                 <VisualState x:Name="FullView" />
                 <VisualState x:Name="SummaryView">
                     <VisualState.Setters>
-                        <Setter Target="PART_AllDayItemsListScrollHost.Visibility" Value="Collapsed" />
+                        <Setter Target="SingleAllDayEventHolder.Visibility" Value="Collapsed" />
-                        <Setter Target="PART_AllDayItemsList.Visibility" Value="Collapsed" />
                         <Setter Target="AllDayItemsSummaryButton.Visibility" Value="Visible" />
                         <Setter Target="AllDayItemsSummaryButton.Content">
                             <Setter.Value>
@@ -47,6 +47,9 @@
                             </Setter.Value>
                         </Setter>
                     </VisualState.Setters>
+                    <VisualState.StateTriggers>
+                        <StateTrigger IsActive="{x:Bind helpers:XamlHelpers.IsMultiple(EventCollection.AllDayEvents.Count), Mode=OneWay, FallbackValue='False'}" />
+                    </VisualState.StateTriggers>
                 </VisualState>
             </VisualStateGroup>
         </VisualStateManager.VisualStateGroups>

Wino.Calendar/Controls/AllDayItemsControl.xaml.cs

@@ -1,19 +1,15 @@
 using Windows.UI.Xaml;
 using Windows.UI.Xaml.Controls;
 using Wino.Core.Domain.Collections;
-using Wino.Core.Domain.Interfaces;
 
 
 namespace Wino.Calendar.Controls
 {
     public sealed partial class AllDayItemsControl : UserControl
     {
-        private const string STATE_SummaryView = "SummaryView";
-        private const string STATE_FullView = "FullView";
-
         #region Dependency Properties
 
-        public static readonly DependencyProperty EventCollectionProperty = DependencyProperty.Register(nameof(EventCollection), typeof(CalendarEventCollection), typeof(AllDayItemsControl), new PropertyMetadata(null, new PropertyChangedCallback(OnAllDayEventsChanged)));
+        public static readonly DependencyProperty EventCollectionProperty = DependencyProperty.Register(nameof(EventCollection), typeof(CalendarEventCollection), typeof(AllDayItemsControl), new PropertyMetadata(null));
         public static readonly DependencyProperty AllDayEventTemplateProperty = DependencyProperty.Register(nameof(AllDayEventTemplate), typeof(DataTemplate), typeof(AllDayItemsControl), new PropertyMetadata(null));
         public static readonly DependencyProperty RegularEventItemTemplateProperty = DependencyProperty.Register(nameof(RegularEventItemTemplate), typeof(DataTemplate), typeof(AllDayItemsControl), new PropertyMetadata(null));
 
@@ -51,58 +47,5 @@ namespace Wino.Calendar.Controls
         {
             InitializeComponent();
         }
-
-        private static void OnAllDayEventsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
-        {
-            if (d is AllDayItemsControl control)
-            {
-                if (e.OldValue != null && e.OldValue is CalendarEventCollection oldCollection)
-                {
-                    control.UnregisterEventCollectionChanged(oldCollection);
-                }
-
-                if (e.NewValue != null && e.NewValue is CalendarEventCollection newCollection)
-                {
-                    control.RegisterEventCollectionChanged(newCollection);
-                }
-
-                control.UpdateCollectionVisuals();
-            }
-        }
-
-        private void RegisterEventCollectionChanged(CalendarEventCollection collection)
-        {
-            collection.CalendarItemAdded += SingleEventUpdated;
-            collection.CalendarItemRemoved += SingleEventUpdated;
-
-            collection.CalendarItemsCleared += EventsCleared;
-        }
-
-        private void UnregisterEventCollectionChanged(CalendarEventCollection collection)
-        {
-            collection.CalendarItemAdded -= SingleEventUpdated;
-            collection.CalendarItemRemoved -= SingleEventUpdated;
-
-            collection.CalendarItemsCleared -= EventsCleared;
-        }
-
-        private void SingleEventUpdated(object sender, ICalendarItem calendarItem) => UpdateCollectionVisuals();
-        private void EventsCleared(object sender, System.EventArgs e) => UpdateCollectionVisuals();
-
-        private void UpdateCollectionVisuals()
-        {
-            if (EventCollection == null) return;
-
-            if (EventCollection.AllDayEvents.Count > 1)
-            {
-                // Summarize
-                VisualStateManager.GoToState(this, STATE_SummaryView, false);
-            }
-            else
-            {
-                // Full view.
-                VisualStateManager.GoToState(this, STATE_FullView, false);
-            }
-        }
     }
 }

Wino.Calendar/Controls/CalendarItemControl.xaml

@@ -0,0 +1,48 @@
+<UserControl
+    x:Class="Wino.Calendar.Controls.CalendarItemControl"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:helpers="using:Wino.Helpers"
+    xmlns:local="using:Wino.Calendar.Controls"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    d:DesignHeight="300"
+    d:DesignWidth="400"
+    mc:Ignorable="d">
+
+    <Grid
+        x:Name="MainGrid"
+        BorderBrush="{ThemeResource CalendarSeperatorBrush}"
+        BorderThickness="1"
+        CornerRadius="6">
+        <Grid x:Name="MainBackground" Background="{x:Bind helpers:XamlHelpers.GetSolidColorBrushFromHex(CalendarItem.AssignedCalendar.BackgroundColorHex), Mode=OneWay}" />
+        <TextBlock
+            x:Name="EventTitleTextblock"
+            Margin="2,0"
+            HorizontalAlignment="Center"
+            VerticalAlignment="Center"
+            Foreground="{x:Bind helpers:XamlHelpers.GetReadableTextColor(CalendarItem.AssignedCalendar.BackgroundColorHex), Mode=OneWay}"
+            Text="{x:Bind CalendarItem.Title}"
+            TextWrapping="Wrap" />
+
+        <VisualStateManager.VisualStateGroups>
+            <VisualStateGroup x:Name="EventDurationStates">
+                <VisualState x:Name="RegularEvent" />
+                <VisualState x:Name="AllDayEvent">
+                    <VisualState.Setters>
+                        <Setter Target="MainGrid.MinHeight" Value="25" />
+                        <Setter Target="EventTitleTextblock.Margin" Value="6,0" />
+                    </VisualState.Setters>
+                </VisualState>
+
+                <VisualState x:Name="MultiDayEvent">
+                    <VisualState.Setters>
+                        <Setter Target="MainBackground.Opacity" Value="0.6" />
+                        <Setter Target="MainGrid.CornerRadius" Value="0" />
+                        <Setter Target="MainGrid.BorderThickness" Value="0.5" />
+                    </VisualState.Setters>
+                </VisualState>
+            </VisualStateGroup>
+        </VisualStateManager.VisualStateGroups>
+    </Grid>
+</UserControl>

Wino.Calendar/Controls/CalendarItemControl.xaml.cs

@@ -0,0 +1,49 @@
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Controls;
+using Wino.Calendar.ViewModels.Data;
+using Wino.Core.Domain.Interfaces;
+
+namespace Wino.Calendar.Controls
+{
+    public sealed partial class CalendarItemControl : UserControl
+    {
+        public ICalendarItem CalendarItem
+        {
+            get { return (CalendarItemViewModel)GetValue(CalendarItemProperty); }
+            set { SetValue(CalendarItemProperty, value); }
+        }
+
+        public static readonly DependencyProperty CalendarItemProperty = DependencyProperty.Register(nameof(CalendarItem), typeof(ICalendarItem), typeof(CalendarItemControl), new PropertyMetadata(null, new PropertyChangedCallback(OnCalendarItemChanged)));
+
+        public CalendarItemControl()
+        {
+            InitializeComponent();
+        }
+
+        private static void OnCalendarItemChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            if (d is CalendarItemControl control)
+            {
+                control.UpdateVisualStates();
+            }
+        }
+
+        private void UpdateVisualStates()
+        {
+            if (CalendarItem == null) return;
+
+            if (CalendarItem.IsAllDayEvent)
+            {
+                VisualStateManager.GoToState(this, "AllDayEvent", true);
+            }
+            else if (CalendarItem.IsMultiDayEvent)
+            {
+                VisualStateManager.GoToState(this, "MultiDayEvent", true);
+            }
+            else
+            {
+                VisualStateManager.GoToState(this, "RegularEvent", true);
+            }
+        }
+    }
+}

Wino.Calendar/Styles/WinoCalendarResources.xaml

@@ -13,19 +13,7 @@
 
     <!--  Default Calendar Item View Model Template  -->
     <DataTemplate x:Key="CalendarItemViewModelItemTemplate" x:DataType="data:CalendarItemViewModel">
-        <Grid
+        <controls:CalendarItemControl CalendarItem="{x:Bind}" />
-            Background="{x:Bind helpers:XamlHelpers.GetSolidColorBrushFromHex(AssignedCalendar.BackgroundColorHex), Mode=OneWay}"
-            BorderBrush="{ThemeResource CalendarSeperatorBrush}"
-            BorderThickness="1"
-            CornerRadius="6">
-            <TextBlock
-                Margin="2,0"
-                HorizontalAlignment="Center"
-                VerticalAlignment="Center"
-                Foreground="{x:Bind helpers:XamlHelpers.GetReadableTextColor(AssignedCalendar.BackgroundColorHex), Mode=OneWay}"
-                Text="{x:Bind CalendarItem.Title}"
-                TextWrapping="Wrap" />
-        </Grid>
     </DataTemplate>
 
     <!--  All-Day Event template  -->
@@ -46,6 +34,11 @@
     <!--  Vertical panel that renders items on canvas.  -->
     <DataTemplate x:Key="DayCalendarItemVerticalRenderTemplate" x:DataType="models:CalendarDayModel">
         <ItemsControl ItemTemplate="{StaticResource CalendarItemViewModelItemTemplate}" ItemsSource="{x:Bind EventsCollection.RegularEvents}">
+            <ItemsControl.ItemContainerTransitions>
+                <TransitionCollection>
+                    <PaneThemeTransition Edge="Left" />
+                </TransitionCollection>
+            </ItemsControl.ItemContainerTransitions>
             <ItemsControl.ItemsPanel>
                 <ItemsPanelTemplate>
                     <controls:WinoCalendarPanel HourHeight="{Binding Path=CalendarRenderOptions.CalendarSettings.HourHeight}" Period="{Binding Path=Period}" />
@@ -229,12 +222,12 @@
                             <!--  All-Day Events  -->
 
                             <!--  TODO: This control leaks.  -->
-                            <!--<controls:AllDayItemsControl
+                            <controls:AllDayItemsControl
                                 Grid.Row="1"
                                 Grid.ColumnSpan="2"
-                                AllDayEventTemplate="{StaticResource AllDayEventItemTemplate}"
+                                AllDayEventTemplate="{StaticResource CalendarItemViewModelItemTemplate}"
                                 EventCollection="{Binding EventsCollection}"
-                                RegularEventItemTemplate="{StaticResource CalendarItemViewModelItemTemplate}" />-->
+                                RegularEventItemTemplate="{StaticResource CalendarItemViewModelItemTemplate}" />
                         </Grid>
 
                         <VisualStateManager.VisualStateGroups>

Wino.Calendar/Wino.Calendar.csproj

@@ -139,6 +139,9 @@
     <Compile Include="Controls\AllDayItemsControl.xaml.cs">
       <DependentUpon>AllDayItemsControl.xaml</DependentUpon>
     </Compile>
+    <Compile Include="Controls\CalendarItemControl.xaml.cs">
+      <DependentUpon>CalendarItemControl.xaml</DependentUpon>
+    </Compile>
     <Compile Include="Controls\CustomCalendarFlipView.cs" />
     <Compile Include="Controls\DayColumnControl.cs" />
     <Compile Include="Controls\DayHeaderControl.cs" />
@@ -250,6 +253,10 @@
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>
     </Page>
+    <Page Include="Controls\CalendarItemControl.xaml">
+      <SubType>Designer</SubType>
+      <Generator>MSBuild:Compile</Generator>
+    </Page>
     <Page Include="MainPage.xaml">
       <Generator>MSBuild:Compile</Generator>
       <SubType>Designer</SubType>

Wino.Core.Domain/Collections/CalendarEventCollection.cs

@@ -26,9 +26,10 @@ namespace Wino.Core.Domain.Collections
 
         public CalendarEventCollection(ITimePeriod period)
         {
+            Period = period;
+
             RegularEvents = new ReadOnlyObservableCollection<ICalendarItem>(_internalRegularEvents);
             AllDayEvents = new ReadOnlyObservableCollection<ICalendarItem>(_internalAllDayEvents);
-            Period = period;
         }
 
         public bool HasCalendarEvent(AccountCalendar accountCalendar)

Wino.Core.Domain/Entities/Calendar/CalendarItem.cs

@@ -38,6 +38,22 @@ namespace Wino.Core.Domain.Entities.Calendar
             }
         }
 
+        public bool IsAllDayEvent
+        {
+            get
+            {
+                return StartDate.TimeOfDay == TimeSpan.Zero && EndDate.TimeOfDay == TimeSpan.Zero;
+            }
+        }
+
+        public bool IsMultiDayEvent
+        {
+            get
+            {
+                return StartDate.Date != EndDate.Date;
+            }
+        }
+
         public double DurationInSeconds { get; set; }
         public string Recurrence { get; set; }
 

Wino.Core.Domain/Interfaces/ICalendarItem.cs

@@ -12,5 +12,7 @@ namespace Wino.Core.Domain.Interfaces
         DateTime EndDate { get; }
         double DurationInSeconds { get; set; }
         ITimePeriod Period { get; }
+        bool IsAllDayEvent { get; }
+        bool IsMultiDayEvent { get; }
     }
 }

Wino.Core.UWP/Helpers/XamlHelpers.cs

@@ -10,7 +10,9 @@ using Windows.UI.Xaml.Controls;
 using Windows.UI.Xaml.Markup;
 using Windows.UI.Xaml.Media;
 using Wino.Core.Domain;
+using Wino.Core.Domain.Collections;
 using Wino.Core.Domain.Enums;
+using Wino.Core.Domain.Interfaces;
 using Wino.Core.Domain.Models.MailItem;
 using Wino.Core.UWP.Controls;
 
@@ -23,6 +25,12 @@ namespace Wino.Helpers
 
         #region Converters
 
+        public static bool IsMultiple(int count) => count > 1;
+        public static bool ReverseIsMultiple(int count) => count < 1;
+
+        public static ICalendarItem GetFirstAllDayEvent(CalendarEventCollection collection)
+            => collection.AllDayEvents.FirstOrDefault();
+
         public static Visibility ReverseBoolToVisibilityConverter(bool value) => value ? Visibility.Collapsed : Visibility.Visible;
         public static Visibility ReverseVisibilityConverter(Visibility visibility) => visibility == Visibility.Visible ? Visibility.Collapsed : Visibility.Visible;
         public static bool ReverseBoolConverter(bool value) => !value;