[No0000124]WPF 扩展控件Behavior的几种方式

一、使用Attached Dependency Property的方式

（1）定义Attached Dependency Property

 public static class DigitsOnlyBehavior
    {
        public static bool GetIsDigitOnly(DependencyObject obj)
        {
            return (bool)obj.GetValue(IsDigitOnlyProperty);
        }

        public static void SetIsDigitOnly(DependencyObject obj, bool value)
        {
            obj.SetValue(IsDigitOnlyProperty, value);
        }

        public static readonly DependencyProperty IsDigitOnlyProperty =
          DependencyProperty.RegisterAttached("IsDigitOnly",
          typeof(bool), typeof(DigitsOnlyBehavior),
          new PropertyMetadata(false, OnIsDigitOnlyChanged));

        private static void OnIsDigitOnlyChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            // ignoring error checking
            var textBox = (TextBox)sender;
            var isDigitOnly = (bool)(e.NewValue);

            if (isDigitOnly)
                textBox.PreviewTextInput += BlockNonDigitCharacters;
            else
                textBox.PreviewTextInput -= BlockNonDigitCharacters;
        }

        private static void BlockNonDigitCharacters(object sender, TextCompositionEventArgs e)
        {
            e.Handled = e.Text.Any(ch => !Char.IsDigit(ch));
        }
    }

使用上面定义好的Attached Dependency Property

<TextBox Grid.Row="0" behaviors:DigitsOnlyBehavior.IsDigitOnly="True" Margin="6"/>

二、使用Behavior<T>

（1） 定义Behavior

public class DragBehavior : Behavior<UIElement>
{
    private Point elementStartPosition;
    private Point mouseStartPosition;
    private TranslateTransform transform = new TranslateTransform();

    protected override void OnAttached()
    {
        Window parent = Application.Current.MainWindow;
        AssociatedObject.RenderTransform = transform;

        AssociatedObject.MouseLeftButtonDown += (sender, e) => 
        {
            elementStartPosition = AssociatedObject.TranslatePoint( new Point(), parent );
            mouseStartPosition = e.GetPosition(parent);
            AssociatedObject.CaptureMouse();
        };

        AssociatedObject.MouseLeftButtonUp += (sender, e) =>
        {
            AssociatedObject.ReleaseMouseCapture();
        };

        AssociatedObject.MouseMove += (sender, e) =>
        {
            Vector diff = e.GetPosition( parent ) - mouseStartPosition;
            if (AssociatedObject.IsMouseCaptured)
            {
                transform.X = diff.X;
                transform.Y = diff.Y;
            }
        };
    }
}

（2）使用Behavior

<Border Background="LightBlue" >
    <e:Interaction.Behaviors>
        <b:DragBehavior/>
    </e:Interaction.Behaviors>
    <TextBlock Text="Drag me around!" />
</Border>