Added MyCustomControl sample

src/Samples/AvaloniaMarkupSample/App.cs

@@ -29,5 +29,5 @@ AppBuilder.Configure<Application>()
                 ))
             .Title(tb1.GetObservable(TextBox.TextProperty).Select(x => x.ToUpper()).ToBinding());
 
-        wnd.Topmost = true;
+        //wnd.Topmost = true;
     }, args);

src/Samples/AvaloniaMarkupSample/HotReloadableView.cs

@@ -1,14 +1,25 @@
 public class HotReloadView : ViewBase
 {
     protected override object Build() =>
-        new Grid()
-            .Background(Brushes.SaddleBrown)
+        new StackPanel()
+            .Width(300)
             .Children(
                 new TextBlock()
                     .Foreground(Brushes.White)
                     .Padding(12)
                     .FontSize(30)
                     .HorizontalAlignment(HorizontalAlignment.Center)
-                    .Text("Hello Hot Reload!")
+                    .Text("Hello Hot Reload!"),
+
+                new TextBlock()
+                    .Text("Custom control example:"),
+
+                new Border()
+                    .BorderBrush(Brushes.Gray)
+                    .BorderThickness(1)
+                    .Child(
+                    new MyCustomControl()
+                        .Margin(20)
+                    )
             );
 }

src/Samples/AvaloniaMarkupSample/MyCustomControl.cs

@@ -0,0 +1,120 @@
+public class MyCustomControl : ViewBase
+{
+    #region NewValue Styled Avalonia Property
+    public string? NewValue
+    {
+        get { return GetValue(NewValueProperty); }
+        set { SetValue(NewValueProperty, value); }
+    }
+
+    public static readonly StyledProperty<string?> NewValueProperty =
+        AvaloniaProperty.Register<MyCustomControl, string?>
+        (
+            nameof(NewValue)
+        );
+    #endregion NewValue Styled Avalonia Property
+
+
+    #region SavedValue Styled Avalonia Property
+    public string? SavedValue
+    {
+        get { return GetValue(SavedValueProperty); }
+        set { SetValue(SavedValueProperty, value); }
+    }
+
+    public static readonly StyledProperty<string?> SavedValueProperty =
+        AvaloniaProperty.Register<MyCustomControl, string?>
+        (
+            nameof(SavedValue)
+        );
+    #endregion SavedValue Styled Avalonia Property
+
+
+    #region CanSave Direct Avalonia Property
+    private bool _canSave = default;
+
+    public static readonly DirectProperty<MyCustomControl, bool> CanSaveProperty =
+        AvaloniaProperty.RegisterDirect<MyCustomControl, bool>
+        (
+            nameof(CanSave),
+            o => o.CanSave
+        );
+
+    public bool CanSave
+    {
+        get => _canSave;
+        private set
+        {
+            SetAndRaise(CanSaveProperty, ref _canSave, value);
+        }
+    }
+
+    #endregion CanSave Direct Avalonia Property
+
+    // CanSave is set to true when SavedValue is not the same as NewView
+    // false otherwise
+    private void SetCanSave(object? _)
+    {
+        CanSave = SavedValue != NewValue;
+    }
+
+    public MyCustomControl()
+    {
+        this.GetObservable(NewValueProperty).Subscribe(SetCanSave);
+        this.GetObservable(SavedValueProperty).Subscribe(SetCanSave);
+    }
+
+    public void Save()
+    {
+        SavedValue = NewValue;
+    }
+
+    public void Cancel()
+    {
+        NewValue = SavedValue;
+    }
+
+    protected override object Build()
+        => new Grid()
+            .Rows("Auto, Auto, *, Auto")
+            .Children(
+                new StackPanel()
+                    .Orientation(Orientation.Horizontal)
+                    .VerticalAlignment(VerticalAlignment.Center)
+                    .Children(
+                        new TextBlock().Text("Enter text:")
+                            .VerticalAlignment(VerticalAlignment.Center),
+                        new TextBox()
+                            .Text(Bind(NewValueProperty))
+                            .MinWidth(150)
+                    ),
+
+                new StackPanel().Row(1)
+                    .Margin(0, 10)
+                    .Orientation(Orientation.Horizontal)
+                    .VerticalAlignment(VerticalAlignment.Center)
+                    .HorizontalAlignment(HorizontalAlignment.Left)
+                    .Children(
+                        new TextBlock().Text("Saved text:")
+                            .VerticalAlignment(VerticalAlignment.Center),
+                        new TextBox()
+                            .Text(Bind(SavedValueProperty))
+                            .MinWidth(150)
+                    ),
+                new StackPanel().Row(3)
+                    .Orientation(Orientation.Horizontal)
+                    .HorizontalAlignment(HorizontalAlignment.Right)
+                    .Children(
+                        new Button().Content("Cancel")
+                            .Margin(5, 0)
+                            .IsEnabled(Bind(CanSaveProperty))
+                            .Command(Bind(this, "Cancel")),
+                        new Button().Content("Save")
+                            .Margin(5, 0)
+                            .IsEnabled(Bind(CanSaveProperty))
+                            .Command(Bind(this, "Save"))
+
+                    )
+            );
+
+}