Added ValueChanged event for RatingBar - Fixes #1027 (#1029)

Added ValueChangedEvent for RatingBar

Author: dhilmathy

MainDemo.Wpf/Buttons.xaml

@@ -572,7 +572,7 @@
         <TextBlock Margin="0 32 0 0" Grid.Row="9" Style="{StaticResource MaterialDesignHeadlineTextBlock}">Rating bar</TextBlock>
         <StackPanel Grid.Row="10" Margin="0 16 0 0" Orientation="Horizontal">
             <smtx:XamlDisplay Key="buttons_58" VerticalContentAlignment="Top" Margin="5 0 0 5">
-                <materialDesign:RatingBar Value="3" x:Name="BasicRatingBar" />
+                <materialDesign:RatingBar Value="3" x:Name="BasicRatingBar"  ValueChanged="BasicRatingBar_ValueChanged"/>
             </smtx:XamlDisplay>
             <TextBlock Text="{Binding ElementName=BasicRatingBar, Path=Value, StringFormat=Rating: {0}}" VerticalAlignment="Top" Margin="10,2,0,0" />
             <smtx:XamlDisplay Key="buttons_59" Margin="24 0 0 5">

MainDemo.Wpf/Buttons.xaml.cs

@@ -1,17 +1,8 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
+using System;
+using System.Diagnostics;
 using System.Windows;
 using System.Windows.Controls;
-using System.Windows.Data;
-using System.Windows.Documents;
 using System.Windows.Input;
-using System.Windows.Media;
-using System.Windows.Media.Imaging;
-using System.Windows.Navigation;
-using System.Windows.Shapes;
 using MaterialDesignColors.WpfExample.Domain;
 
 namespace MaterialDesignColors.WpfExample
@@ -24,7 +15,6 @@ public partial class Buttons : UserControl
         public Buttons()
         {
             InitializeComponent();
-
             FloatingActionDemoCommand = new AnotherCommandImplementation(Execute);
         }
 
@@ -36,9 +26,9 @@ private void Execute(object o)
         }
 
         private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
-	    {
+	{
             Console.WriteLine("Just checking we haven't suppressed the button.");
-		}
+	}
 
         private void PopupBox_OnOpened(object sender, RoutedEventArgs e)
         {
@@ -58,7 +48,11 @@ private void CountingButton_OnClick(object sender, RoutedEventArgs e)
             var next = int.Parse(CountingBadge.Badge.ToString()) + 1;
 
             CountingBadge.Badge = next < 21 ? (object)next : null;
-
+        }
+        
+        private void BasicRatingBar_ValueChanged(object sender, RoutedPropertyChangedEventArgs<int> e)
+        {
+            Debug.WriteLine($"BasicRatingBar value changed from {e.OldValue} to {e.NewValue}.");
         }
     }
 }

MaterialDesignThemes.Wpf/RatingBar.cs

@@ -1,14 +1,6 @@
-using System;
-using System.Collections.Generic;
 using System.Collections.ObjectModel;
-using System.ComponentModel;
-using System.Linq;
-using System.Runtime.CompilerServices;
-using System.Text;
-using System.Threading.Tasks;
 using System.Windows;
 using System.Windows.Controls;
-using System.Windows.Data;
 using System.Windows.Input;
 
 namespace MaterialDesignThemes.Wpf
@@ -64,8 +56,10 @@ public int Max
 
         private static void ValuePropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
         {
-            foreach (var button in ((RatingBar) dependencyObject).RatingButtons)
+            var ratingBar = (RatingBar)dependencyObject;
+            foreach (var button in ratingBar.RatingButtons)
                 button.IsWithinSelectedValue = button.Value <= (int)dependencyPropertyChangedEventArgs.NewValue;
+            OnValueChanged(ratingBar, dependencyPropertyChangedEventArgs);
         }
 
         public int Value
@@ -74,6 +68,30 @@ public int Value
             set { SetValue(ValueProperty, value); }
         }
 
+        public static readonly RoutedEvent ValueChangedEvent =
+            EventManager.RegisterRoutedEvent(
+                nameof(Value),
+                RoutingStrategy.Bubble,
+                typeof(RoutedPropertyChangedEventHandler<int>),
+                typeof(RatingBar));
+
+        public event RoutedPropertyChangedEventHandler<int> ValueChanged
+        {
+            add => AddHandler(ValueChangedEvent, value);
+            remove => RemoveHandler(ValueChangedEvent, value);
+        }
+
+        private static void OnValueChanged(
+            DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            var instance = (RatingBar)d;
+            var args = new RoutedPropertyChangedEventArgs<int>(
+                    (int)e.OldValue,
+                    (int)e.NewValue) 
+                { RoutedEvent = ValueChangedEvent };
+            instance.RaiseEvent(args);
+        }
+
         public ReadOnlyObservableCollection<RatingBarButton> RatingButtons => _ratingButtons;
 
         public static readonly DependencyProperty ValueItemContainerButtonStyleProperty = DependencyProperty.Register(