New expander control.

Wino.Mail/Controls/WinoExpander.cs

@@ -1,17 +1,43 @@
-using Microsoft.UI.Xaml.Controls;
-using Windows.UI.Xaml.Controls.Primitives;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Controls;
+using Windows.UI.Xaml.Markup;
 
 namespace Wino.Controls
 {
-    public class WinoExpander : Expander
+    [ContentProperty(Name = nameof(Content))]
+    public class WinoExpander : Control
     {
-        protected override void OnApplyTemplate()
+        public static readonly DependencyProperty HeaderProperty = DependencyProperty.Register(nameof(Header), typeof(UIElement), typeof(WinoExpander), new PropertyMetadata(null));
+        public static readonly DependencyProperty ContentProperty = DependencyProperty.Register(nameof(Content), typeof(UIElement), typeof(WinoExpander), new PropertyMetadata(null));
+        public static readonly DependencyProperty IsExpandedProperty = DependencyProperty.Register(nameof(IsExpanded), typeof(bool), typeof(WinoExpander), new PropertyMetadata(false, new PropertyChangedCallback(OnIsExpandedChanged)));
+
+        public bool IsExpanded
         {
-            base.OnApplyTemplate();
-            if (GetTemplateChild("ExpanderHeader") is ToggleButton toggleButton)
-            {
-                toggleButton.Padding = new Windows.UI.Xaml.Thickness(0, 4, 0, 4);
-            }
+            get { return (bool)GetValue(IsExpandedProperty); }
+            set { SetValue(IsExpandedProperty, value); }
+        }
+
+        public UIElement Content
+        {
+            get { return (UIElement)GetValue(ContentProperty); }
+            set { SetValue(ContentProperty, value); }
+        }
+
+        public UIElement Header
+        {
+            get { return (UIElement)GetValue(HeaderProperty); }
+            set { SetValue(HeaderProperty, value); }
+        }
+
+        private static void OnIsExpandedChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
+        {
+            if (obj is WinoExpander control)
+                control.UpdateVisualStates();
+        }
+
+        private void UpdateVisualStates()
+        {
+            VisualStateManager.GoToState(this, IsExpanded ? "Expanded" : "Collapsed", true);
         }
     }
 }