Improve numerical binding error messages.

samples/BindingTest/MainWindow.xaml

@@ -82,6 +82,7 @@
         <StackPanel Margin="18" Gap="4" MinWidth="200" DataContext="{Binding DataAnnotationsValidation}">
           <TextBlock FontSize="16" Text="Data Annotations Validation"/>
           <TextBox Watermark="Phone #" UseFloatingWatermark="True" Text="{Binding PhoneNumber}"/>
+          <TextBox Watermark="Less Than 10" UseFloatingWatermark="True" Text="{Binding Path=LessThan10}"/>
         </StackPanel>
       </StackPanel>
     </TabItem>

samples/BindingTest/ViewModels/DataAnnotationsErrorViewModel.cs

@@ -10,5 +10,8 @@ namespace BindingTest.ViewModels
         [Phone]
         [MaxLength(10)]
         public string PhoneNumber { get; set; }
+
+        [Range(0, 9)]
+        public int LessThan10 { get; set; }
     }
 }

src/Avalonia.Base/AvaloniaObject.cs

@@ -667,7 +667,7 @@ namespace Avalonia
                     Logger.Error(
                         LogArea.Binding,
                         this,
-                        "Error binding to {Target}.{Property}: {Message}",
+                        "Error in binding to {Target}.{Property}: {Message}",
                         this,
                         property,
                         ExceptionUtilities.GetMessage(notification.Error));

src/Avalonia.Base/PriorityValue.cs

@@ -189,7 +189,7 @@ namespace Avalonia
                 LogEventLevel.Error,
                 LogArea.Binding,
                 _owner,
-                "Error binding to {Target}.{Property}: {Message}",
+                "Error in binding to {Target}.{Property}: {Message}",
                 _owner,
                 Property,
                 error.Error.Message);

src/Avalonia.Base/Utilities/TypeUtilities.cs

@@ -27,6 +27,21 @@ namespace Avalonia.Utilities
             { typeof(short), new List<Type> { typeof(byte) } }
         };
 
+        private static readonly Type[] NumericTypes = new[]
+        {
+            typeof(Byte),
+            typeof(Decimal),
+            typeof(Double),
+            typeof(Int16),
+            typeof(Int32),
+            typeof(Int64),
+            typeof(SByte),
+            typeof(Single),
+            typeof(UInt16),
+            typeof(UInt32),
+            typeof(UInt64),
+        };
+
         /// <summary>
         /// Returns a value indicating whether null can be assigned to the specified type.
         /// </summary>
@@ -208,5 +223,31 @@ namespace Avalonia.Utilities
                 return null;
             }
         }
+
+        /// <summary>
+        /// Determines if a type is numeric.  Nullable numeric types are considered numeric.
+        /// </summary>
+        /// <returns>
+        /// True if the type is numberic; otherwise false.
+        /// </returns>
+        /// <remarks>
+        /// Boolean is not considered numeric.
+        /// </remarks>
+        public static bool IsNumeric(Type type)
+        {
+            if (type == null)
+            {
+                return false;
+            }
+
+            if (type.GetTypeInfo().IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>))
+            {
+                return IsNumeric(Nullable.GetUnderlyingType(type));
+            }
+            else
+            {
+                return NumericTypes.Contains(type);
+            }
+        }
     }
 }

src/Markup/Avalonia.Markup/Data/ExpressionSubject.cs

@@ -139,9 +139,6 @@ namespace Avalonia.Markup.Data
                                 "IValueConverter should not return non-errored BindingNotification.");
                         }
 
-                        notification.Error = new InvalidCastException(
-                            $"Error setting '{_inner.Expression}': {notification.Error.Message}");
-                        notification.ErrorType = BindingErrorType.Error;
                         _errors.OnNext(notification);
 
                         if (_fallbackValue != AvaloniaProperty.UnsetValue)

src/Markup/Avalonia.Markup/DefaultValueConverter.cs

@@ -43,7 +43,17 @@ namespace Avalonia.Markup
 
             if (value != null)
             {
-                var message = $"Could not convert '{value}' to '{targetType}'";
+                string message;
+
+                if (TypeUtilities.IsNumeric(targetType))
+                {
+                    message = $"'{value}' is not a valid number.";
+                }
+                else
+                {
+                    message = $"Could not convert '{value}' to '{targetType.Name}'.";
+                }
+
                 return new BindingNotification(new InvalidCastException(message), BindingErrorType.Error);
             }
 

tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs

@@ -332,7 +332,7 @@ namespace Avalonia.Base.UnitTests
             var target = new Class1();
             var source = new Subject<object>();
             var called = false;
-            var expectedMessageTemplate = "Error binding to {Target}.{Property}: {Message}";
+            var expectedMessageTemplate = "Error in binding to {Target}.{Property}: {Message}";
 
             LogCallback checkLogMessage = (level, area, src, mt, pv) =>
             {

tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Direct.cs

@@ -437,7 +437,7 @@ namespace Avalonia.Base.UnitTests
             {
                 if (level == LogEventLevel.Error &&
                     area == LogArea.Binding &&
-                    mt == "Error binding to {Target}.{Property}: {Message}" &&
+                    mt == "Error in binding to {Target}.{Property}: {Message}" &&
                     pv.Length == 3 &&
                     pv[0] is Class1 &&
                     object.ReferenceEquals(pv[1], Class1.FooProperty) &&

tests/Avalonia.Markup.UnitTests/Data/ExpressionSubjectTests.cs

@@ -123,7 +123,7 @@ namespace Avalonia.Markup.UnitTests.Data
 
             Assert.Equal(
                 new BindingNotification(
-                    new InvalidCastException("Could not convert 'foo' to 'System.Int32'"),
+                    new InvalidCastException("'foo' is not a valid number."),
                     BindingErrorType.Error,
                     42),
                 result);
@@ -144,7 +144,7 @@ namespace Avalonia.Markup.UnitTests.Data
 
             Assert.Equal(
                 new BindingNotification(
-                    new InvalidCastException("Could not convert 'foo' to 'System.Int32'"),
+                    new InvalidCastException("'foo' is not a valid number."),
                     BindingErrorType.Error,
                     42),
                 result);
@@ -294,7 +294,7 @@ namespace Avalonia.Markup.UnitTests.Data
                     new BindingNotification("1.2"),
                     new BindingNotification("3.4"),
                     new BindingNotification(
-                        new InvalidCastException("Error setting 'DoubleValue': Could not convert 'bar' to 'System.Double'"),
+                        new InvalidCastException("'bar' is not a valid number."),
                         BindingErrorType.Error)
                 },
                 result);

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlBindingTests.cs

@@ -39,7 +39,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             {
                 if (level == LogEventLevel.Error &&
                     area == LogArea.Binding &&
-                    mt == "Error binding to {Target}.{Property}: {Message}" &&
+                    mt == "Error in binding to {Target}.{Property}: {Message}" &&
                     pv.Length == 3 &&
                     pv[0] is ProgressBar &&
                     object.ReferenceEquals(pv[1], ProgressBar.ValueProperty) &&