In `Avalonia.ReactiveUI`, simplified null checks for delegate invocations (#13023)

Co-authored-by: Lehonti Ramos <lehonti@ramos>

src/Avalonia.Controls/AutoCompleteBox/AutoCompleteBox.cs

@@ -1490,10 +1490,7 @@ namespace Avalonia.Controls
             _view?.AddRange(_newViewItems);
 
             // Clear the evaluator to discard a reference to the last item
-            if (_valueBindingEvaluator != null)
-            {
-                _valueBindingEvaluator.ClearDataContext();
-            }
+            _valueBindingEvaluator?.ClearDataContext();
 
             // indicate that filtering is not ongoing anymore
             _filterInAction = false;

src/Avalonia.Controls/Calendar/Calendar.cs

@@ -2059,10 +2059,7 @@ namespace Avalonia.Controls
             Debug.Assert(e.NewValue is bool, "NewValue should be a boolean!");
             bool isEnabled = (bool)e.NewValue;
 
-            if (MonthControl != null)
-            {
-                MonthControl.UpdateDisabled(isEnabled);
-            }
+            MonthControl?.UpdateDisabled(isEnabled);
         }
 
         static Calendar()

src/Avalonia.Controls/DefinitionBase.cs

@@ -72,7 +72,7 @@ namespace Avalonia.Controls
             LayoutWasUpdated = true;
 
             //  defer verification for shared definitions
-            if (_sharedState != null) { _sharedState.EnsureDeferredValidation(grid); }
+            _sharedState?.EnsureDeferredValidation(grid);
         }
 
         /// <summary>

src/Avalonia.Controls/Documents/InlineCollection.cs

@@ -140,10 +140,7 @@ namespace Avalonia.Controls.Documents
         /// </summary>
         protected void Invalidate()
         {
-            if (InlineHost != null)
-            {
-                InlineHost.Invalidate();
-            }
+            InlineHost?.Invalidate();
 
             Invalidated?.Invoke(this, EventArgs.Empty);
         }
@@ -154,15 +151,9 @@ namespace Avalonia.Controls.Documents
             {
                 if (oldParent != newParent)
                 {
-                    if (oldParent != null)
-                    {
-                        oldParent.Remove(child);
-                    }
-
-                    if (newParent != null)
-                    {
-                        newParent.Add(child);
-                    }
+                    oldParent?.Remove(child);
+
+                    newParent?.Add(child);
                 }
             }
         }

src/Avalonia.Controls/Flyouts/PopupFlyoutBase.cs

@@ -256,10 +256,7 @@ namespace Avalonia.Controls.Primitives
                 else
                 {
                     var nextFocus = KeyboardNavigationHandler.GetNext(Popup.Child, NavigationDirection.Next);
-                    if (nextFocus != null)
-                    {
-                        nextFocus.Focus();
-                    }
+                    nextFocus?.Focus();
                 }
             }
             else if (ShowMode == FlyoutShowMode.TransientWithDismissOnPointerMoveAway)

src/Avalonia.Controls/Primitives/Popup.cs

@@ -750,10 +750,7 @@ namespace Avalonia.Controls.Primitives
                 else
                 {
                     var anc = this.FindLogicalAncestorOfType<Control>();
-                    if (anc != null)
-                    {
-                        anc.Focus();
-                    }
+                    anc?.Focus();
                 }
             }
         }

src/Avalonia.Controls/Primitives/Track.cs

@@ -229,18 +229,12 @@ namespace Avalonia.Controls.Primitives
                 offset = offset.WithY(isDirectionReversed ? decreaseButtonLength + thumbLength : 0.0);
                 pieceSize = pieceSize.WithHeight(increaseButtonLength);
 
-                if (IncreaseButton != null)
-                {
-                    IncreaseButton.Arrange(new Rect(offset, pieceSize));
-                }
+                IncreaseButton?.Arrange(new Rect(offset, pieceSize));
 
                 offset = offset.WithY(isDirectionReversed ? 0.0 : increaseButtonLength + thumbLength);
                 pieceSize = pieceSize.WithHeight(decreaseButtonLength);
 
-                if (DecreaseButton != null)
-                {
-                    DecreaseButton.Arrange(new Rect(offset, pieceSize));
-                }
+                DecreaseButton?.Arrange(new Rect(offset, pieceSize));
 
                 offset = offset.WithY(isDirectionReversed ? decreaseButtonLength : increaseButtonLength);
                 pieceSize = pieceSize.WithHeight(thumbLength);
@@ -264,18 +258,12 @@ namespace Avalonia.Controls.Primitives
                 offset = offset.WithX(isDirectionReversed ? increaseButtonLength + thumbLength : 0.0);
                 pieceSize = pieceSize.WithWidth(decreaseButtonLength);
 
-                if (DecreaseButton != null)
-                {
-                    DecreaseButton.Arrange(new Rect(offset, pieceSize));
-                }
+                DecreaseButton?.Arrange(new Rect(offset, pieceSize));
 
                 offset = offset.WithX(isDirectionReversed ? 0.0 : decreaseButtonLength + thumbLength);
                 pieceSize = pieceSize.WithWidth(increaseButtonLength);
 
-                if (IncreaseButton != null)
-                {
-                    IncreaseButton.Arrange(new Rect(offset, pieceSize));
-                }
+                IncreaseButton?.Arrange(new Rect(offset, pieceSize));
 
                 offset = offset.WithX(isDirectionReversed ? increaseButtonLength : decreaseButtonLength);
                 pieceSize = pieceSize.WithWidth(thumbLength);

src/Avalonia.Controls/SplitButton/SplitButton.cs

@@ -144,10 +144,7 @@ namespace Avalonia.Controls
         /// </summary>
         protected void OpenFlyout()
         {
-            if (Flyout != null)
-            {
-                Flyout.ShowAt(this);
-            }
+            Flyout?.ShowAt(this);
         }
 
         /// <summary>
@@ -155,10 +152,7 @@ namespace Avalonia.Controls
         /// </summary>
         protected void CloseFlyout()
         {
-            if (Flyout != null)
-            {
-                Flyout.Hide();
-            }
+            Flyout?.Hide();
         }
 
         /// <summary>