WPF中的依赖属性和附加属性

public delegate bool ValidateValueCallback(object value)

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   public partial class MainWindow
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   {
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   public MainWindow()
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   {
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   InitializeComponent();
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   SetTextBinding();
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   }
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    private void SetTextBinding()
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    {
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    var binding = new Binding
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    {
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    Source = this,
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    Path = new PropertyPath("MyAge")
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    };
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    TestTextBox.SetBinding(TextBox.TextProperty, binding);
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    }
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    public int MyAge
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    {
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    get { return (int)GetValue(MyAgeProperty); }
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    set { SetValue(MyAgeProperty, value); }
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    }
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    //这里注册一个MyAge的依赖属性用于前台绑定，指定默认值为18
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    public static readonly DependencyProperty MyAgeProperty =
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    DependencyProperty.Register("MyAge", typeof(int), typeof(MainWindow),
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    new PropertyMetadata(18, PropertyChangedCallback, CoerceValueCallback), ValidateValueCallback);
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    //当赋值成功的时候就改变TextBox的边框颜色
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    private static void PropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
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    {
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    var window = dependencyObject as Window;
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    var textBox = window?.FindName("TestTextBox") as TextBox;
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    if (textBox != null) textBox.BorderBrush = Brushes.Cyan;
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    }
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    //当进行赋值的时候，如果值不在18~100之间，强制将值恢复为18，表示该值不合要求
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    private static object CoerceValueCallback(DependencyObject dependencyObject, object baseValue)
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    {
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    var value = (int)baseValue;
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    return value < 18 ? 18 : value;
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    }
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    //在开始赋值前对值进行检查，如果值超过100就弹个错误框显示
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    private static bool ValidateValueCallback(object o)
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    {
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    var value = (int)o;
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    if (value > 100)
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    MessageBox.Show("年龄有点大哈");
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    return value < 100;
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    }
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55.  
    //当儿童选项被勾选的时候去更改属性的元数据
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    private void ChildCheckBox_OnChecked(object sender, RoutedEventArgs e)
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    {
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    ChildAge.Instance.ChangeMetadata(sender);
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    }
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    //当取消勾选的时候，应该恢复为原来的属性值绑定才能正确显示
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    private void ChildCheckBox_OnUnchecked(object sender, RoutedEventArgs e)
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    {
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    SetTextBinding();
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    }
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    }
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    //重新定义一个Child类继承MainWindow
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    public class ChildAge : MainWindow
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    {
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    public static ChildAge Instance
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    {
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    get { return _instance ?? (_instance = new ChildAge()); }
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    }
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    private static ChildAge _instance;
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78.  
    private static Window _containerWindow;
79.  
    public void ChangeMetadata(object sender)
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    {
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    var item = sender as CheckBox;
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    if (item == null) return;
83.  
     
84.  
    //更改属性元数据，默认值为1，对应的值处理检查方法也需重新定义
85.  
    MyAgeProperty.OverrideMetadata(typeof(ChildAge),
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    new PropertyMetadata(1, ChildAgePropertyChangedCallback, ChildCoerceValueCallback));
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    ///////////这里因为前台数据是和后台绑定的，因此如果对应的属性改变了，前台绑定的源也应该随之改变
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    _containerWindow = GetWindow(item);
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    if (_containerWindow != null)
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    {
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    var binding = new Binding
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    {
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    Source = this,
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    Path = new PropertyPath("MyAge")
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    };
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    var textBox = _containerWindow.FindName("TestTextBox") as TextBox;
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    textBox?.SetBinding(TextBox.TextProperty, binding);
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    }
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     }
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102.  
     private static object ChildCoerceValueCallback(DependencyObject dependencyObject, object baseValue)
103.  
     {
104.  
     var value = (int)baseValue;
105.  
     return (value < 1 || value >= 18) ? 1 : value;
106.  
     }
107.  
      
108.  
     private static void ChildAgePropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
109.  
     {
110.  
     var textBox = _containerWindow?.FindName("TestTextBox") as TextBox;
111.  
     if (textBox != null) textBox.BorderBrush = Brushes.DarkGreen;
112.  
     }
113.  
     }