Add docs and clean up

src/Avalonia.Controls/Button.cs

@@ -79,6 +79,9 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<bool> IsPressedProperty =
             AvaloniaProperty.Register<Button, bool>(nameof(IsPressed));
 
+        /// <summary>
+        /// Defines the <see cref="Flyout"/> property
+        /// </summary>
         public static readonly DirectProperty<Button, FlyoutBase> FlyoutProperty =
             AvaloniaProperty.RegisterDirect<Button, FlyoutBase>(nameof(Flyout),
                 x => x.Flyout, (x, v) => x.Flyout = v);
@@ -175,6 +178,9 @@ namespace Avalonia.Controls
             private set { SetValue(IsPressedProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets the Flyout that should be shown with this button
+        /// </summary>
         public FlyoutBase Flyout
         {
             get => _flyout;

src/Avalonia.Controls/Flyouts/Flyout.cs

@@ -1,10 +1,5 @@
-using System;
-using System.Collections.Generic;
-using System.Collections.Specialized;
-using System.Text;
-using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Primitives;
 using Avalonia.Metadata;
-using Avalonia.Styling;
 
 #nullable enable
 
@@ -12,13 +7,22 @@ namespace Avalonia.Controls
 {
     public class Flyout : FlyoutBase
     {
+        /// <summary>
+        /// Defines the <see cref="Content"/> property
+        /// </summary>
         public static readonly StyledProperty<object> ContentProperty =
             AvaloniaProperty.Register<Flyout, object>(nameof(Content));
 
+        /// <summary>
+        /// Gets the Classes collection to applied to the FlyoutPresenter this Flyout is hosting
+        /// </summary>
         public Classes? FlyoutPresenterClasses => _classes ??= new Classes();
 
         private Classes? _classes;
 
+        /// <summary>
+        /// Gets or sets the content to display in this flyout
+        /// </summary>
         [Content]
         public object Content
         {

src/Avalonia.Controls/Flyouts/FlyoutBase.cs

@@ -15,20 +15,35 @@ namespace Avalonia.Controls.Primitives
             Control.ContextFlyoutProperty.Changed.Subscribe(OnContextFlyoutPropertyChanged);
         }
 
+        /// <summary>
+        /// Defines the <see cref="IsOpen"/> property
+        /// </summary>
         private static readonly DirectProperty<FlyoutBase, bool> IsOpenProperty =
            AvaloniaProperty.RegisterDirect<FlyoutBase, bool>(nameof(IsOpen),
                x => x.IsOpen);
 
+        /// <summary>
+        /// Defines the <see cref="Target"/> property
+        /// </summary>
         public static readonly DirectProperty<FlyoutBase, Control?> TargetProperty =
             AvaloniaProperty.RegisterDirect<FlyoutBase, Control?>(nameof(Target), x => x.Target);
 
+        /// <summary>
+        /// Defines the <see cref="Placement"/> property
+        /// </summary>
         public static readonly StyledProperty<FlyoutPlacementMode> PlacementProperty =
             AvaloniaProperty.Register<FlyoutBase, FlyoutPlacementMode>(nameof(Placement));
 
+        /// <summary>
+        /// Defines the <see cref="ShowMode"/> property
+        /// </summary>
         public static readonly DirectProperty<FlyoutBase, FlyoutShowMode> ShowModeProperty =
             AvaloniaProperty.RegisterDirect<FlyoutBase, FlyoutShowMode>(nameof(ShowMode),
                 x => x.ShowMode, (x, v) => x.ShowMode = v);
 
+        /// <summary>
+        /// Defines the AttachedFlyout property
+        /// </summary>
         public static readonly AttachedProperty<FlyoutBase?> AttachedFlyoutProperty =
             AvaloniaProperty.RegisterAttached<FlyoutBase, Control, FlyoutBase?>("AttachedFlyout", null);
 
@@ -39,24 +54,36 @@ namespace Avalonia.Controls.Primitives
         Rect? enlargedPopupRect;
         IDisposable? transientDisposable;
 
+        /// <summary>
+        /// Gets whether this Flyout is currently Open
+        /// </summary>
         public bool IsOpen
         {
             get => _isOpen;
             private set => SetAndRaise(IsOpenProperty, ref _isOpen, value);
         }
 
+        /// <summary>
+        /// Gets or sets the desired placement
+        /// </summary>
         public FlyoutPlacementMode Placement
         {
             get => GetValue(PlacementProperty);
             set => SetValue(PlacementProperty, value);
         }
 
+        /// <summary>
+        /// Gets or sets the desired ShowMode
+        /// </summary>
         public FlyoutShowMode ShowMode
         {
             get => _showMode;
             set => SetAndRaise(ShowModeProperty, ref _showMode, value);
         }
 
+        /// <summary>
+        /// Gets the Target used for showing the Flyout
+        /// </summary>
         public Control? Target
         {
             get => _target;
@@ -84,16 +111,29 @@ namespace Avalonia.Controls.Primitives
             flyout?.ShowAt(flyoutOwner);
         }
 
+        /// <summary>
+        /// Shows the Flyout at the given Control
+        /// </summary>
+        /// <param name="placementTarget">The control to show the Flyout at</param>
         public void ShowAt(Control placementTarget)
         {
             ShowAtCore(placementTarget);
         }
 
+        /// <summary>
+        /// Shows the Flyout for the given control at the current pointer location, as in a ContextFlyout
+        /// </summary>
+        /// <param name="placementTarget">The target control</param>
+        /// <param name="showAtPointer">True to show at pointer</param>
         public void ShowAt(Control placementTarget, bool showAtPointer)
         {
             ShowAtCore(placementTarget, showAtPointer);
         }
 
+        /// <summary>
+        /// Hides the Flyout
+        /// </summary>
+        /// <param name="canCancel">Whether or not this closing action can be cancelled</param>
         public void Hide(bool canCancel = true)
         {
             if (!IsOpen)
@@ -253,6 +293,10 @@ namespace Avalonia.Controls.Primitives
             Closed?.Invoke(this, null);
         }
 
+        /// <summary>
+        /// Used to create the content the Flyout displays
+        /// </summary>
+        /// <returns></returns>
         protected abstract Control CreatePresenter();
 
         private void InitPopup()
@@ -416,8 +460,7 @@ namespace Avalonia.Controls.Primitives
                         c.ContextFlyout.ShowAt(c, true);
                     }
                 }
-            }
-            
+            }            
         }
     }
 }

src/Avalonia.Controls/Flyouts/FlyoutPlacementMode.cs

@@ -1,8 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-
-namespace Avalonia.Controls
+namespace Avalonia.Controls
 {
     public enum FlyoutPlacementMode
     {

src/Avalonia.Controls/Flyouts/FlyoutPresenter.cs

@@ -1,8 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-
-namespace Avalonia.Controls
+namespace Avalonia.Controls
 {
     public class FlyoutPresenter : ContentControl
     {

src/Avalonia.Controls/Flyouts/MenuFlyout.cs

@@ -1,11 +1,8 @@
 using System.Collections;
-using System.Collections.Specialized;
 using Avalonia.Collections;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
-using Avalonia.Input;
 using Avalonia.Metadata;
-using Avalonia.Styling;
 
 #nullable enable
 
@@ -18,16 +15,25 @@ namespace Avalonia.Controls
             _items = new AvaloniaList<object>();
         }
 
+        /// <summary>
+        /// Defines the <see cref="Items"/> property
+        /// </summary>
         public static readonly DirectProperty<MenuFlyout, IEnumerable> ItemsProperty =
             ItemsControl.ItemsProperty.AddOwner<MenuFlyout>(x => x.Items,
                 (x, v) => x.Items = v);
 
+        /// <summary>
+        /// Defines the <see cref="ItemTemplate"/> property
+        /// </summary>
         public static readonly DirectProperty<MenuFlyout, IDataTemplate?> ItemTemplateProperty =
             AvaloniaProperty.RegisterDirect<MenuFlyout, IDataTemplate?>(nameof(ItemTemplate),
                 x => x.ItemTemplate, (x, v) => x.ItemTemplate = v);
 
         public Classes? FlyoutPresenterClasses => _classes ??= new Classes();
 
+        /// <summary>
+        /// Gets or sets the items of the MenuFlyout
+        /// </summary>
         [Content]
         public IEnumerable Items
         {
@@ -35,6 +41,9 @@ namespace Avalonia.Controls
             set => SetAndRaise(ItemsProperty, ref _items, value);
         }
 
+        /// <summary>
+        /// Gets or sets the template used for the items
+        /// </summary>
         public IDataTemplate? ItemTemplate
         {
             get => _itemTemplate;