这段代码位于UserControl对象的类声明中.一切正常 – 它编译和运行完美.

public static System.Windows.DependencyProperty DepProp
    = System.Windows.DependencyProperty.Register(   "Rect",typeof(System.Windows.Shapes.Rectangle),typeof(FooControl));
public System.Windows.Shapes.Rectangle Rect
{
    get
    { return ((System.Windows.Shapes.Rectangle)(GetValue(DepProp))); }
    set
    { SetValue(DepProp,value); }
}

但是,当我将默认值添加到依赖项属性时：
代码编译,但在尝试实例化UserControl时崩溃并发生致命异常.

作为参考,我的代码现在看起来像这样 – 添加了PropertyMetaData行：

public static System.Windows.DependencyProperty DepProp
    = System.Windows.DependencyProperty.Register(   "Rect",typeof(FooControl),new System.Windows.PropertyMetadata(new System.Windows.Shapes.Rectangle()));
public System.Windows.Shapes.Rectangle Rect
{
    get
    { return ((System.Windows.Shapes.Rectangle)(GetValue(DepProp))); }
    set
    { SetValue(DepProp,value); }
}

从调用Register()中删除PropertyMetadata会导致程序完美运行,不会出现任何崩溃或任何其他问题.但我需要以后代码的默认值.如何让它接受默认值而不会崩溃？

当它崩溃时,输出窗口中会显示以下异常：

A first chance exception of type 'System.ArgumentException' occurred in WindowsBase.dll  
A first chance exception of type 'System.Reflection.TargetInvocationException' occurred in mscorlib.dll  
A first chance exception of type 'System.Windows.Markup.XamlParseException' occurred in PresentationFramework.dll

我需要尽快开始工作,所以任何建议都会很棒！