private bool isDragging = false;

private void DragStart(object sender, MouseButtonEventArgs args)
{
Shape draggable = sender as Shape;
if (draggable != null)
{
isDragging = true;
draggable.CaptureMouse();
}
}
private void DragDelta(object sender, MouseEventArgs args)
{
Shape draggable = sender as Shape;
if (draggable != null && isDragging)
{
Point currentPosition = args.GetPosition(null);
TranslateTransform transform = draggable.RenderTransform
as TranslateTransform;
if (transform == null)
{
transform = new TranslateTransform();
draggable.RenderTransform = transform;
}

transform.X = (currentPosition.X - draggable.Width / 2);
transform.Y = (currentPosition.Y - draggable.Height / 2);
}
}

private void DragComplete(object sender, MouseButtonEventArgs args)
{
Shape draggable = sender as Shape;
if (draggable != null)
{
isDragging = false;
draggable.ReleaseMouseCapture();
}
}

private static void OnHoverChanged(DependencyObject obj,   

DependencyPropertyChangedEventArgs args)
{
Border border = obj as Border;
if (border != null)
{
if(args.OldValue == null && args.NewValue != null)

{
border.MouseEnter +=
SetHoverBackground;
border.MouseLeave +=
SetNotHoverBackground;
}
else if(args.OldValue != null && args.NewValue ==
null)
{
border.MouseEnter -=
SetHoverBackground;
border.MouseLeave -=
SetNotHoverBackground;
}
}
}

private static void OnIsEnabledChanged(DependencyObject obj, 

DependencyPropertyChangedEventArgs args)
{
UIElement dragSource = obj as UIElement;

bool wasEnabled = (args.OldValue != null) ? (bool)args.OldValue : false;
bool isEnabled = (args.NewValue != null) ? (bool)args.NewValue : false;
//如果行为被禁用，移除这个事件处理程序
if (wasEnabled && !isEnabled)
{
dragSource.MouseLeftButtonDown -= DragStart;
}
//如果行为被附加，添加这个事件处理程序
if (!wasEnabled && isEnabled)
{
dragSource.MouseLeftButtonDown += DragStart;
}
}

public static readonly DependencyProperty XProperty = 

DependencyProperty.RegisterAttached(
"X",
typeof(double),
typeof(DragDropBehavior),
new PropertyMetadata(double.NaN));

public static readonly DependencyProperty YProperty =
DependencyProperty.RegisterAttached(
"Y",
typeof(double),
typeof(DragDropBehavior),
new PropertyMetadata(double.NaN));

private static void DragStart(object sender, MouseButtonEventArgs args)

{
UIElement dragSource = sender as UIElement;
//创建执行拖动操作的TranslateTransform
TranslateTransform dragTransform = new TranslateTransform();
dragTransform.X = 0;
dragTransform.Y = 0;
//如果是首次使用拖放，先要设置TranslateTransform
dragSource.RenderTransform = (
dragSource.RenderTransform is TranslateTransform) ?
dragSource.RenderTransform : dragTransform;
//分别为MouseMove和MouseLeftButtonUp添加事件处理程序
dragSource.MouseMove += OnDragDelta;
dragSource.MouseLeftButtonUp += OnDragComplete;
//捕获鼠标
dragSource.CaptureMouse();
}

private static void DragDelta(object sender, MouseEventArgs args)

{
FrameworkElement dragSource = sender as FrameworkElement;
//计算dragSource的偏移量，更新TranslateTransform
FrameworkElement dragDropHost = FindDragDropHost(dragSource);
Point relativeLocationInHost = args.GetPosition(dragDropHost);
Point relativeLocationInSource = args.GetPosition(dragSource);
//获得当前位置
double xPosition = GetX(dragSource);
double yPosition = GetY(dragSource);
//从前一次位置计算变数
double xChange = relativeLocationInHost.X - xPosition;
double yChange = relativeLocationInHost.Y - yPosition;
//如果这不是首次鼠标移动，更新位置
if (!double.IsNaN(xPosition))
{
((TranslateTransform)dragSource.RenderTransform).X +=
xChange;
}

if (!double.IsNaN(yPosition))
{
((TranslateTransform)dragSource.RenderTransform).Y +=
yChange;
}
//更新你的私有附加属性跟踪拖动位置
SetX(dragSource, relativeLocationInHost.X);
SetY(dragSource, relativeLocationInHost.Y);
}

private static void DragComplete(object sender, 

MouseButtonEventArgs args)
{
UIElement dragSource = sender as UIElement;
dragSource.MouseMove -= DragDelta;
dragSource.MouseLeftButtonUp -= DragComplete;
//设置x和y的值，以便下一次MouseDown时好重置
SetX(dragSource, double.NaN);
SetY(dragSource, double.NaN);
//释放鼠标捕获
dragSource.ReleaseMouseCapture();
}
这个新的迭代实现克服了前面描述的限制，它也允许流畅跟踪鼠标，在新的实现中，你只需要把鼠标放在
拖动项目的中心，在前面的实现中，鼠标需要保持放在容器里面。
public static FrameworkElement FindDragDropHost(
UIElement element)
{
DependencyObject parent = VisualTreeHelper.GetParent(element);
while (parent != null && !GetIsHost(parent))
{
parent = VisualTreeHelper.GetParent(parent);
}
return parent as FrameworkElement;
}