将一个类别的值绑定到另一个类别的另一个值

Question

我有以下类别gist with the classes。
我想将Item.Visible绑定到Items.ItemsVisible--是否有可能？如果是这样 - 如何？

Item.cs：

using System; 
using System.ComponentModel; 

namespace WpfApplication85 
{ 
    /// <summary> 
    /// Item Object. 
    /// </summary> 
    public class Item : INotifyPropertyChanged 
    { 
     #region INotifyPropertyChanged 

     public event PropertyChangedEventHandler PropertyChanged; //Event to notify when Property changed. 

     /// <summary> 
     /// Notify that Property has Changed. 
     /// </summary> 
     /// <param name="propertyName">The name of the Property</param> 
     protected void NotifyPropertyChanged(string propertyName) 
     { 
      if (PropertyChanged != null) 
      { 
       PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); 
      } 
     } 

     #endregion 

     #region Private Variables 

     private bool _Visible; //Bool to determine if the Item is visible or not 

     #endregion 

     #region Public Properties 

     //Return the value of Visible/Set the value of Visible and Notify. 
     public bool Visible 
     { 
      get { return _Visible; } 
      set 
      { 
       _Visible = value; 
       NotifyPropertyChanged("Visible"); 
      } 
     } 

     #endregion 

     #region Constructor 

     /// <summary> 
     /// Item Constructor 
     /// </summary> 
     public Item() 
     { 
      _Visible = true; 
     } 

     #endregion 
    } 
} 

Items.cs：

using System; 
using System.Collections.ObjectModel; 
using System.ComponentModel; 

namespace WpfApplication85 
{ 
    /// <summary> 
    /// Items Object. 
    /// </summary> 
    public class Items : INotifyPropertyChanged 
    { 
     #region INotifyPropertyChanged 

     public event PropertyChangedEventHandler PropertyChanged; //Event to notify when Property changed. 

     /// <summary> 
     /// Notify that Property has Changed. 
     /// </summary> 
     /// <param name="propertyName">The name of the Property</param> 
     protected void NotifyPropertyChanged(string propertyName) 
     { 
      if (PropertyChanged != null) 
      { 
       PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); 
      } 
     } 

     #endregion 

     #region Private Variables 

     private bool _itemsVisible; //Bool to determine if the Items are visible or not 
     private ObservableCollection<Item> _itemsCollection; //Collection of Items. 

     #endregion 

     #region Public Properties 

     //Return the value of ItemsVisible/Set the value of ItemsVisible and Notify. 
     public bool ItemsVisible 
     { 
      get { return _itemsVisible; } 
      set 
      { 
       _itemsVisible = value; 
       NotifyPropertyChanged("ItemsVisible"); 
      } 
     } 

     //Return the Items Collection/Set the Items Collection and Notify. 
     public ObservableCollection<Item> ItemsCollection 
     { 
      get 
      { 
       return _itemsCollection; 
      } 
      set 
      { 
       _itemsCollection = value; 
       NotifyPropertyChanged("ItemsCollection"); 
      } 
     } 

     #endregion 

     #region Constructor 

     /// <summary> 
     /// Items Constructor 
     /// </summary> 
     public Items() 
     { 
      _itemsVisible = true; 
      _itemsCollection = new ObservableCollection<Item>(); 
     } 

     #endregion 

     #region Methods 

     /// <summary> 
     /// Add Item to the ItemsCollection. 
     /// </summary> 
     /// <param name="item">Item Object</param> 
     public void AddItem(Item item) 
     { 
      //Bind item.Visible to this.ItemsVisible 
      _itemsCollection.Add(item); 
     } 

     #endregion 
    } 
} 

Answer 1

在Items和Item属性中设置数据绑定只是从正确的接口监听PropertyChanged或CollectionChanged事件。

您可以使用+=子句认购，或WeakEventListener模式，使用PropertyChangedEventManager和CollectionChangedEventManager

我喜欢最后一个，因为：

监听事件可能会导致内存泄漏。

所以，你Items类应该实现IWeakEventListener接口：

public class Items : INotifyPropertyChanged, IWeakEventListener 
{ 
    #region IWeakEventListener 

    public bool ReceiveWeakEvent(Type managerType, Object sender, EventArgs e) 
    { 
     if (sender == this._itemsCollection && managerType == typeof(CollectionChangedEventManager)) 
     { 
      // Your collection has changed, you should add/remove 
      // subscription for PropertyChanged event 
      UpdateSubscriptions((NotifyCollectionChangedEventArgs)e); 
      return true; 
     } 
     if (sender is Item && managerType == typeof(PropertyChangedEventManager)) 
     { 
      // The Visible property of an Item object has changed 
      // You should handle it properly here, for example, like this: 
      this.ItemsVisible = this._itemsCollection.All(i => i.Visible); 
      return true; 
     } 

     return false; 
    } 

    private void UpdateSubscriptions(NotifyCollectionChangedEventArgs e) 
    { 
     switch(e.Action) 
     { 
      case NotifyCollectionChangedAction.Add: 
       foreach (Item item in e.NewItems) 
       { 
        PropertyChangedEventManager.AddListener(item, this, "Visible"); 
       } 
       break; 
      case NotifyCollectionChangedAction.Remove: 
       foreach (Item item in e.OldItems) 
       { 
        PropertyChangedEventManager.RemoveListener(item, this, "Visible"); 
       } 
       break; 
      case NotifyCollectionChangedAction.Reset: 
       foreach (Item item in this._itemsCollection) 
       { 
        PropertyChangedEventManager.RemoveListener(item, this, "Visible"); 
        PropertyChangedEventManager.AddListener(item, this, "Visible"); 
       } 
       break; 
      default: 
       break; 
     } 
    } 

... 
    public Items() 
    { 
     _itemsVisible = true; 
     _itemsCollection = new ObservableCollection<Item>(); 
     CollectionChangedEventManager.AddListener(_itemsCollection, this); 
    } 
} 

Answer 2

在WPF意义仅适用于DependencyProperties和两个标准性能（即使使用INotifyPropertyChanged的时候）之间不适用绑定。也就是说，如果您将这些类用作View Models并将它们绑定到控件，那么当ItemsVisible和Visible属性都为true时（例如），您可以使用MultiConverter将控件的可见性设置为折叠。

或者，您可以将一个Parent属性添加到Item类并将其设置为父项目类，它将允许您让Item.Visible属性返回父项的ItemsVisible属性（或者在应用程序中再次使用任何逻辑）。