Initial integration.

Wino.Mail.WinUI/Selectors/CustomAreaCalendarItemSelector.cs

@@ -0,0 +1,21 @@
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+using Wino.Calendar.ViewModels.Data;
+
+namespace Wino.Calendar.Selectors;
+
+public partial class CustomAreaCalendarItemSelector : DataTemplateSelector
+{
+    public DataTemplate AllDayTemplate { get; set; }
+    public DataTemplate MultiDayTemplate { get; set; }
+
+    protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
+    {
+        if (item is CalendarItemViewModel calendarItemViewModel)
+        {
+            return calendarItemViewModel.IsMultiDayEvent ? MultiDayTemplate : AllDayTemplate;
+        }
+
+        return base.SelectTemplateCore(item, container);
+    }
+}