Question

我在asp.net应用程序中使用ObservableCollection，通过使用“CollectionChanged”事件，我可以获得添加/删除的值。为此，我将对象存储在会话（InProc）中，每个工作正常。

现在问题是我将会话更改为outproc（DB），Collection_CollectionChanged停止触发（Button2_Click）。我认为必须要对序列化做些什么。对此有任何帮助。

示例的用法：首先点击button1＆amp;然后按钮2，按钮1和按钮1

后面的aspx代码中有2个事件

  [Serializable]
    public class School
    {
        public School()
        {
            studentList = new ObservableCollection<Student>();            
            studentList.CollectionChanged += Collection_CollectionChanged;
        }
        public string SchoolName { get; set;}
        public ObservableCollection<Student> studentList { get; set; }
        public void Collection_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
        {
           if (e.Action == NotifyCollectionChangedAction.Add)
            {
                var result= "add";
            }
           else if (e.Action == NotifyCollectionChangedAction.Remove)
           {
               var result=  "del";
           }
        }
    }

    [Serializable]
    public class Student
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }
    //Code in .aspx.cs Page
    protected void Button1_Click(object sender, EventArgs e)
    {
        School school = new School();
        school.SchoolName = "Benie";
        school.studentList.Add(new Student() { FirstName = "a", LastName = "a1" });
        school.studentList.Add(new Student() { FirstName = "b", LastName = "b1" });
        Session["school"] = school;
    }
    protected void Button2_Click(object sender, EventArgs e)
    {
        School school = Session["school"] as School;
        //Not working in Out Proc session, Working in InProc session
        school.studentList.RemoveAt(1);
    }

Answer 1

我怀疑CollectionChanged事件没有被挂钩，因为该对象是通过序列化创建的（奇怪但我认为可能）或者序列化后没有挂钩Button1_Click（更高的可能性因为你没有在构造函数中这样做，但是我另读了你的问题）

要解决此问题，您可以尝试为您的School类实现ISerializable（不要忘记构造函数）并将事件挂钩到序列化构造函数中。

Answer 2

我同意问题肯定是序列化，特别是Student对象被ObservableCollection包装的事实。如果要继续使用该方法，可以自己实现自定义序列化。

Kent Bogart有一篇关于这个确切场景以及如何在ObservableCollections上实现自定义序列化的帖子。 Take a look at it here.

Answer 3

问题是，CollectionChanged事件未标记为“不可序列化”。因此，在反序列化后，CollectionChanged为null。解决方案here

[Serializable]
public class SObservableCollection<T> : ObservableCollection<T>, 
    INotifyPropertyChanged
{
    [field:NonSerialized]
    public override event NotifyCollectionChangedEventHandler CollectionChanged;

    [field: NonSerialized]
    private PropertyChangedEventHandler _propertyChangedEventHandler;

    event PropertyChangedEventHandler INotifyPropertyChanged.PropertyChanged
    {
        add
        {
            _propertyChangedEventHandler = Delegate.Combine(_propertyChangedEventHandler, value) as PropertyChangedEventHandler;
        }
        remove
        {
            _propertyChangedEventHandler = Delegate.Remove(_propertyChangedEventHandler, value) as PropertyChangedEventHandler;
        }
    }

    protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
    {
        NotifyCollectionChangedEventHandler handler = CollectionChanged;

        if (handler != null)
        {
            handler(this, e);
        }
    }

    protected override void OnPropertyChanged(PropertyChangedEventArgs e)
    {
        PropertyChangedEventHandler handler = _propertyChangedEventHandler;

        if (handler != null)
        {
            handler(this, e);
        }
    }
}

ObservableCollection“CollectionChanged”未在OutProc会话状态中触发

3 个答案: