模仿microsoft实现依赖属性

//传入ownerType增加Owner public DependencyProperty AddOwner(Type ownerType) { return AddOwner (ownerType, null); } //增加所有者,根据ownerType和typeMetadata public DependencyProperty AddOwner(Type ownerType, PropertyMetadata typeMetadata) { if (typeMetadata == null) typeMetadata = new Pr