扩展集合ObservableCollection使集合在添加、删除、值变更后触发事件

概述

ObservableCollection继承了INotifyPropertyChanged接口，在属性变更时可以通知界面，当我把ObservableCollection集合绑定到界面的DataGrid后，我希望在界面修改表格数值后，可以触发一个 事件来验证我界面设定数据的有效性，但是对于集合的添加、删除只会触发集合的get属性，值重置不会触发集合的get、set属性，这时候我们就需要扩展ObservableCollection集合.

集合扩展

  • 代码如下：重写OnCollectionChanged方法，使得集合改变(增添、删除、改变)时拥有属性变更事件
  1. using System;
  2. using System.Collections;
  3. using System.Collections.Specialized;
  4. using System.ComponentModel;
  5. using DevExpress.Xpo;
  7. namespace Caliburn.Micro.Hello
  8. {
  9.     public class ItemsChangeObservableCollection<T> :
  10.             System.Collections.ObjectModel.ObservableCollection<T> where T : INotifyPropertyChanged
  11.     {
  12.         protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
  13.         {
  14.             if (e.Action == NotifyCollectionChangedAction.Add)
  15.             {
  16.                 RegisterPropertyChanged(e.NewItems);
  17.             }
  18.             else if (e.Action == NotifyCollectionChangedAction.Remove)
  19.             {
  20.                 UnRegisterPropertyChanged(e.OldItems);
  21.             }
  22.             else if (e.Action == NotifyCollectionChangedAction.Replace)
  23.             {
  24.                 UnRegisterPropertyChanged(e.OldItems);
  25.                 RegisterPropertyChanged(e.NewItems);
  26.             }
  28.             base.OnCollectionChanged(e);
  29.         }
  31.         protected override void ClearItems()
  32.         {
  33.             UnRegisterPropertyChanged(this);
  34.             base.ClearItems();
  35.         }
  37.         private void RegisterPropertyChanged(IList items)
  38.         {
  39.             foreach (INotifyPropertyChanged item in items)
  40.             {
  41.                 if (item != null)
  42.                 {
  43.                     item.PropertyChanged += new PropertyChangedEventHandler(item_PropertyChanged);
  44.                 }
  45.             }
  46.         }
  48.         private void UnRegisterPropertyChanged(IList items)
  49.         {
  50.             foreach (INotifyPropertyChanged item in items)
  51.             {
  52.                 if (item != null)
  53.                 {
  54.                     item.PropertyChanged -= new PropertyChangedEventHandler(item_PropertyChanged);
  55.                 }
  56.             }
  57.         }
  59.         private void item_PropertyChanged(object sender, PropertyChangedEventArgs e)
  60.         {
  61.             //launch an event Reset with name of property changed
  62.             base.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
  63.         }
  64.     }
  65. }

事件订阅

  • 可以用如下方法订阅事件：
  1. this.StudentList.CollectionChanged += StudentList_OnCollectionChanged;
  2. 或
  3. StudentList.CollectionChanged += new NotifyCollectionChangedEventHandler(StudentList_OnCollectionChanged);
  • 事件方法：
  1. public void StudentList_OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
  2. {
  3.     MessageBox.Show("当前触发的事件是："+ e.Action.ToString());
  4. }
  • 集合定义：
  1. private ItemsChangeObservableCollection<Students> studentList;
  2. public ItemsChangeObservableCollection<Students> StudentList
  3. {
  4.     get
  5.     {
  6.         return studentList;
  7.     }
  8.     set
  9.     {
  10.         studentList = value;
  11.     }
  12. }

参考资料