Always call UpdateDataValidation on notification.

This speeds up the common path of no data validation: this way we don't
need to get the metadata unless a binding notification is received. This
means that if a binding with data validation is assigned to a property
that isn't interested then UpdateDataValidation will be called, but the
control should just ignore it.

src/Avalonia.Base/AvaloniaObject.cs

@@ -658,7 +658,6 @@ namespace Avalonia
         /// <param name="value">The value.</param>
         private void SetDirectValue(AvaloniaProperty property, object value)
         {
-            var metadata = (IDirectPropertyMetadata)property.GetMetadata(GetType());
             var notification = value as BindingNotification;
 
             if (notification != null)
@@ -682,6 +681,7 @@ namespace Avalonia
 
             if (notification == null || notification.HasValue)
             {
+                var metadata = (IDirectPropertyMetadata)property.GetMetadata(GetType());
                 var accessor = (IDirectPropertyAccessor)GetRegistered(property);
                 var finalValue = value == AvaloniaProperty.UnsetValue ? 
                     metadata.UnsetValue : value;
@@ -691,7 +691,7 @@ namespace Avalonia
                 accessor.SetValue(this, finalValue);
             }
 
-            if (metadata.EnableDataValidation && notification != null)
+            if (notification != null)
             {
                 UpdateDataValidation(property, notification);
             }

src/Avalonia.Controls/TextBox.cs

@@ -464,7 +464,10 @@ namespace Avalonia.Controls
 
         protected override void UpdateDataValidation(AvaloniaProperty property, BindingNotification status)
         {
-            ((IPseudoClasses)Classes).Set(":error", status.ErrorType != BindingErrorType.None);
+            if (property == TextProperty)
+            {
+                ((IPseudoClasses)Classes).Set(":error", status.ErrorType != BindingErrorType.None);
+            }
         }
 
         private int CoerceCaretIndex(int value)

tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_DataValidation.cs

@@ -14,10 +14,7 @@ namespace Avalonia.Base.UnitTests
         {
             var target = new Class1();
 
-            target.SetValue(Class1.NonValidatedProperty, new BindingNotification(6));
-            target.SetValue(Class1.NonValidatedProperty, new BindingNotification(new Exception(), BindingErrorType.Error));
-            target.SetValue(Class1.NonValidatedProperty, new BindingNotification(new Exception(), BindingErrorType.DataValidationError));
-            target.SetValue(Class1.NonValidatedProperty, new BindingNotification(7));
+            target.SetValue(Class1.NonValidatedDirectProperty, 6);
 
             Assert.Empty(target.Notifications);
         }
@@ -27,10 +24,7 @@ namespace Avalonia.Base.UnitTests
         {
             var target = new Class1();
 
-            target.SetValue(Class1.NonValidatedDirectProperty, new BindingNotification(6));
-            target.SetValue(Class1.NonValidatedDirectProperty, new BindingNotification(new Exception(), BindingErrorType.Error));
-            target.SetValue(Class1.NonValidatedDirectProperty, new BindingNotification(new Exception(), BindingErrorType.DataValidationError));
-            target.SetValue(Class1.NonValidatedDirectProperty, new BindingNotification(7));
+            target.SetValue(Class1.NonValidatedDirectProperty, 6);
 
             Assert.Empty(target.Notifications);
         }