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

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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.

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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

using System;
using System.Collections;
using System.Collections.Specialized;
using System.ComponentModel;
using DevExpress.Xpo;namespace Caliburn.Micro.Hello
{public class ItemsChangeObservableCollection<T> :System.Collections.ObjectModel.ObservableCollection<T> where T : INotifyPropertyChanged{protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
{if (e.Action == NotifyCollectionChangedAction.Add){RegisterPropertyChanged(e.NewItems);}else if (e.Action == NotifyCollectionChangedAction.Remove){UnRegisterPropertyChanged(e.OldItems);}else if (e.Action == NotifyCollectionChangedAction.Replace){UnRegisterPropertyChanged(e.OldItems);RegisterPropertyChanged(e.NewItems);}base.OnCollectionChanged(e);}protected override void ClearItems()
{UnRegisterPropertyChanged(this);base.ClearItems();}private void RegisterPropertyChanged(IList items)
{foreach (INotifyPropertyChanged item in items){if (item != null){item.PropertyChanged += new PropertyChangedEventHandler(item_PropertyChanged);}}}private void UnRegisterPropertyChanged(IList items)
{foreach (INotifyPropertyChanged item in items){if (item != null){item.PropertyChanged -= new PropertyChangedEventHandler(item_PropertyChanged);}}}private void item_PropertyChanged(object sender, PropertyChangedEventArgs e)
{//launch an event Reset with name of property changedbase.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));}}
}

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事件订阅

可以用如下方法订阅事件：

this.StudentList.CollectionChanged += StudentList_OnCollectionChanged;
或
StudentList.CollectionChanged += new NotifyCollectionChangedEventHandler(StudentList_OnCollectionChanged);

事件方法：

public void StudentList_OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e){MessageBox.Show("当前触发的事件是："+ e.Action.ToString());}

集合定义：

private ItemsChangeObservableCollection<Students> studentList;public ItemsChangeObservableCollection<Students> StudentList{get{return studentList;}set{studentList = value;}}

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效果演示