Swap order of parameters to event args.

As described in #3437 the argument ordering was different to WPF/UWP causing bugs in some code ported from WPF/UWP. Use the same argument ordering as WPF/UWP.

Fixes #3437

src/Avalonia.Controls/AutoCompleteBox.cs

@@ -683,7 +683,7 @@ namespace Avalonia.Controls
                 added.Add(e.NewValue);
             }
 
-            OnSelectionChanged(new SelectionChangedEventArgs(SelectionChangedEvent, added, removed));
+            OnSelectionChanged(new SelectionChangedEventArgs(SelectionChangedEvent, removed, added));
         }
 
         /// <summary>

src/Avalonia.Controls/Calendar/DatePicker.cs

@@ -788,7 +788,7 @@ namespace Avalonia.Controls
                     removedItems.Add(removedDate.Value);
                 }
 
-                handler(this, new SelectionChangedEventArgs(SelectingItemsControl.SelectionChangedEvent, addedItems, removedItems));
+                handler(this, new SelectionChangedEventArgs(SelectingItemsControl.SelectionChangedEvent, removedItems, addedItems));
             }
         }
         private void OnCalendarClosed(EventArgs e)

src/Avalonia.Controls/Calendar/SelectedDatesCollection.cs

@@ -49,7 +49,7 @@ namespace Avalonia.Controls.Primitives
 
         private void InvokeCollectionChanged(System.Collections.IList removedItems, System.Collections.IList addedItems)
         {
-            _owner.OnSelectedDatesCollectionChanged(new SelectionChangedEventArgs(null, addedItems, removedItems));
+            _owner.OnSelectedDatesCollectionChanged(new SelectionChangedEventArgs(null, removedItems, addedItems));
         }
 
         /// <summary>
@@ -119,7 +119,7 @@ namespace Avalonia.Controls.Primitives
                 }
             }
 
-            _owner.OnSelectedDatesCollectionChanged(new SelectionChangedEventArgs(null, _addedItems, _owner.RemovedItems));
+            _owner.OnSelectedDatesCollectionChanged(new SelectionChangedEventArgs(null, _owner.RemovedItems, _addedItems));
             _owner.RemovedItems.Clear();
             _owner.UpdateMonths();
             _isRangeAdded = false;

src/Avalonia.Controls/Primitives/SelectingItemsControl.cs

@@ -939,8 +939,8 @@ namespace Avalonia.Controls.Primitives
             {
                 var changed = new SelectionChangedEventArgs(
                     SelectionChangedEvent,
-                    added ?? Empty,
+                    removed ?? Empty,
-                    removed ?? Empty);
+                    added ?? Empty);
                 RaiseEvent(changed);
             }
         }
@@ -1055,8 +1055,8 @@ namespace Avalonia.Controls.Primitives
 
                 var e = new SelectionChangedEventArgs(
                     SelectionChangedEvent,
-                    added != -1 ? new[] { ElementAt(Items, added) } : Array.Empty<object>(),
+                    removed?.Select(x => ElementAt(Items, x)).ToArray() ?? Array.Empty<object>(),
-                    removed?.Select(x => ElementAt(Items, x)).ToArray() ?? Array.Empty<object>());
+                    added != -1 ? new[] { ElementAt(Items, added) } : Array.Empty<object>());
                 RaiseEvent(e);
             }
 

src/Avalonia.Controls/Repeater/ItemsRepeaterElementIndexChangedEventArgs.cs

@@ -12,11 +12,11 @@ namespace Avalonia.Controls
     /// </summary>
     public class ItemsRepeaterElementIndexChangedEventArgs : EventArgs
     {
-        internal ItemsRepeaterElementIndexChangedEventArgs(IControl element, int newIndex, int oldIndex)
+        internal ItemsRepeaterElementIndexChangedEventArgs(IControl element, int oldIndex, int newIndex)
         {
             Element = element;
-            NewIndex = newIndex;
             OldIndex = oldIndex;
+            NewIndex = newIndex;
         }
 
         /// <summary>

src/Avalonia.Controls/SelectionChangedEventArgs.cs

@@ -16,13 +16,13 @@ namespace Avalonia.Controls
         /// Initializes a new instance of the <see cref="SelectionChangedEventArgs"/> class.
         /// </summary>
         /// <param name="routedEvent">The event being raised.</param>
-        /// <param name="addedItems">The items added to the selection.</param>
         /// <param name="removedItems">The items removed from the selection.</param>
-        public SelectionChangedEventArgs(RoutedEvent routedEvent, IList addedItems, IList removedItems)
+        /// <param name="addedItems">The items added to the selection.</param>
+        public SelectionChangedEventArgs(RoutedEvent routedEvent, IList removedItems, IList addedItems)
             : base(routedEvent)
         {
-            AddedItems = addedItems;
             RemovedItems = removedItems;
+            AddedItems = addedItems;
         }
 
         /// <summary>

src/Avalonia.Controls/TreeView.cs

@@ -324,8 +324,8 @@ namespace Avalonia.Controls
             {
                 var changed = new SelectionChangedEventArgs(
                     SelectingItemsControl.SelectionChangedEvent,
-                    added ?? Empty,
+                    removed ?? Empty,
-                    removed ?? Empty);
+                    added ?? Empty);
                 RaiseEvent(changed);
             }
         }