c# wpf如何附加依赖项属性

public class School : DependencyObject
 { 
  public static int GetGrade(DependencyObject obj)
  {
   return (int)obj.GetValue(GradeProperty);
  }

  public static void SetGrade(DependencyObject obj, int value)
  {
   obj.SetValue(GradeProperty, value);
  }

  // Using a DependencyProperty as the backing store for Grade. This enables animation, styling, binding, etc...
  public static readonly DependencyProperty GradeProperty =
   DependencyProperty.ReGISterAttached("Grade", typeof(int), typeof(School), new PropertyMetadata(0));
 }

public class Person : DependencyObject
 {
  public string IdentityID
  {
   get { return (string)GetValue(IdentityIDProperty); }
   set { SetValue(IdentityIDProperty, value); }
  }

  // Using a DependencyProperty as the backing store for IdentityID. This enables animation, styling, binding, etc...
  public static readonly DependencyProperty IdentityIDProperty =
   DependencyProperty.Register("IdentityID", typeof(string), typeof(Person));

  public string Name
  {
   get { return (string)GetValue(NamePropertyProperty); }
   set { SetValue(NamePropertyProperty, value); }
  }

  // Using a DependencyProperty as the backing store for NameProperty. This enables animation, styling, binding, etc...
  public static readonly DependencyProperty NamePropertyProperty =
   DependencyProperty.Register("Name", typeof(string), typeof(Person)); 

  public DateTime BirthDate
  {
   get { return (DateTime)GetValue(BirthDateProperty); }
   set { SetValue(BirthDateProperty, value); }
  }

  // Using a DependencyProperty as the backing store for BirthDate. This enables animation, styling, binding, etc...
  public static readonly DependencyProperty BirthDateProperty =
   DependencyProperty.Register("BirthDate", typeof(DateTime), typeof(Person)); 

  public bool Gender
  {
   get { return (bool)GetValue(GenderProperty); }
   set { SetValue(GenderProperty, value); }
  }

  // Using a DependencyProperty as the backing store for Gender. This enables animation, styling, binding, etc...
  public static readonly DependencyProperty GenderProperty =
   DependencyProperty.Register("Gender", typeof(bool), typeof(Person)); 

  public string Nation
  {
   get { return (string)GetValue(NationProperty); }
   set { SetValue(NationProperty, value); }
  }

  // Using a DependencyProperty as the backing store for Nation. This enables animation, styling, binding, etc...
  public static readonly DependencyProperty NationProperty =
   DependencyProperty.Register("Nation", typeof(string), typeof(Person));
   
 }

 <Button Content="点击给Pserson对象在对应的业务上附加依赖性属性" Click="AddPsersonAttachedProperty_Click"/>

private void AddPsersonAttachedProperty_Click(object sender, RoutedEventArgs e)
  {
   Person person = new Person();
   School.SetGrade(person, 1);
   var grade = School.GetGrade(person);
   MessageBox.Show(grade.ToString()) ;
  }

 <Canvas>
    <Slider x:Name="sliderX" Canvas.Top="10" Canvas.Left="10" Width="200" Minimum="50" Maximum="200"/>
    <Slider x:Name="sliderY" Canvas.Top="40" Canvas.Left="10" Width="200" Minimum="50" Maximum="200"/>
    <Ellipse Fill="Blue" Width="30" Height="30" Canvas.Left="{Binding ElementName=sliderX,Path=Value}" Canvas.Top="{Binding ElementName=sliderY,Path=Value}"/>
   </Canvas>