C#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


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 changed
            base.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
        }
    }
}

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;
            }
        }

效果演示

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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