WPF/附加属性 - 请解释为什么它有效

发布于 2024-11-14 11:36:03 字数 760 浏览 3 评论 0原文

请帮助我理解值“ABC”的存储位置。当我运行内存分析器时，我没有看到任何 MyClass 实例，事实上绑定有效，并且 GroupBox.Header 获取值 ABC...
感谢您的帮助。

<GroupBox Header="{Binding Path=(local:MyClass.Tag1), RelativeSource={RelativeSource Self}}"  
          local:MyClass.Tag1="ABC" />

public class MyClass
{
    public static readonly DependencyProperty Tag1Property = DependencyProperty.RegisterAttached("Tag1", typeof(object), typeof(MyClass), new UIPropertyMetadata(null));
    public static object GetTag1(DependencyObject obj)
    {
        return obj.GetValue(Tag1Property);
    }
    public static void SetTag1(DependencyObject obj, object value)
    {
        obj.SetValue(Tag1Property, value);
    }
}

原文

Please help me understand where the value "ABC" gets stored. When I run memory profilers I don't see any instance of MyClass, and in fact the binding works and the GroupBox.Header gets the value ABC...

Thanks for your help.

<GroupBox Header="{Binding Path=(local:MyClass.Tag1), RelativeSource={RelativeSource Self}}"  
          local:MyClass.Tag1="ABC" />

public class MyClass
{
    public static readonly DependencyProperty Tag1Property = DependencyProperty.RegisterAttached("Tag1", typeof(object), typeof(MyClass), new UIPropertyMetadata(null));
    public static object GetTag1(DependencyObject obj)
    {
        return obj.GetValue(Tag1Property);
    }
    public static void SetTag1(DependencyObject obj, object value)
    {
        obj.SetValue(Tag1Property, value);
    }
}

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淡紫姑娘！ 2024-11-21 11:36:03

依赖属性在内部维护一个字典。使用稀疏存储机制来存储值。这些属性在类级别关联 - 是静态的。值 ABC 以键值对的形式存储在字典中

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淡水深流 2024-11-21 11:36:03

这是对其工作原理的非常直接的解释： http:// nirajrules.wordpress.com/2009/01/19/inside-dependencyobject-dependencyproperty/

本质上正如 Hasan Fahim 所说，依赖属性被存储在基于属性名称和属性所有者的内部哈希表中。通过将属性存储为与所有者关联，您实际上可以在哈希表中为同一类型的不同对象拥有唯一的整体。这意味着 Get 和 Set 方法不需要是静态的。

示例：

public class Something
{
  public static readonly DependencyProperty IsEditableProperty = DependencyProperty.Register("IsEditable", typeof(Boolean), typeof(ResourceCanvas), new PropertyMetadata(true));

    public Boolean IsEditable
    {
        get { return (Boolean)this.GetValue(IsEditableProperty); }
        set { this.SetValue(IsEditableProperty, value); }
    }
 }

使用版本，我可以实例化 Something 类型的许多实例，每个实例都包含 IsEditable 的“不同”值。

Here is a pretty straight forward explanation of how it works: http://nirajrules.wordpress.com/2009/01/19/inside-dependencyobject-dependencyproperty/

Essentially as Hasan Fahim said, the dependency properties are stored in an internal Hashtable based on the property name and the owner of the property. By storing the property as associated with the owner, you can actually have unique entires in the HashTable for different objects of the same type. This means that the Get and Set methods do not need to be static.

Example:

public class Something
{
  public static readonly DependencyProperty IsEditableProperty = DependencyProperty.Register("IsEditable", typeof(Boolean), typeof(ResourceCanvas), new PropertyMetadata(true));

    public Boolean IsEditable
    {
        get { return (Boolean)this.GetValue(IsEditableProperty); }
        set { this.SetValue(IsEditableProperty, value); }
    }
 }

With version I can instantiate many instances of type Something each containing a "different" value of IsEditable.

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