add ImageAttach

src/Shared/HandyControl_Shared/Controls/Attach/ImageAttach.cs

@@ -0,0 +1,42 @@
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Media;
+
+namespace HandyControl.Controls
+{
+    public class ImageAttach
+    {
+        public static readonly DependencyProperty SourceFailedProperty = DependencyProperty.RegisterAttached(
+            "SourceFailed", typeof(ImageSource), typeof(ImageAttach), new FrameworkPropertyMetadata(default(ImageSource), FrameworkPropertyMetadataOptions.Inherits, OnSourceFailedChanged));
+
+        private static void OnSourceFailedChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+        {
+            if (d is Image image)
+            {
+                if (e.NewValue is ImageSource)
+                {
+                    image.ImageFailed += Image_ImageFailed;
+                }
+                else
+                {
+                    image.ImageFailed -= Image_ImageFailed;
+                }
+            }
+        }
+
+        private static void Image_ImageFailed(object sender, ExceptionRoutedEventArgs e)
+        {
+            if (sender is Image image)
+            {
+                image.SetCurrentValue(Image.SourceProperty, GetSourceFailed(image));
+                image.ImageFailed -= Image_ImageFailed;
+            }
+        }
+
+        public static void SetSourceFailed(DependencyObject element, ImageSource value)
+            => element.SetValue(SourceFailedProperty, value);
+
+        public static ImageSource GetSourceFailed(DependencyObject element)
+            => (ImageSource) element.GetValue(SourceFailedProperty);
+    }
+}

src/Shared/HandyControl_Shared/Controls/Block/ToggleBlock.cs

@@ -8,9 +8,6 @@ namespace HandyControl.Controls
     /// <summary>
     ///     切换块
     /// </summary>
-    /// <remarks>
-    ///     在不需要命中测试的情况下可代替ToggleButton或CheckBox，以减少内存用量。
-    /// </remarks>
     public class ToggleBlock : Control
     {
         public static readonly DependencyProperty IsCheckedProperty = DependencyProperty.Register(