C# 如何从 [Serializable] INotifyPropertyChanged 实现器中排除不可序列化的观察者？

How to exclude nonserializable observers from a [Serializable] INotifyPropertyChanged implementor?

提问by skolima

I have almost a hundred of entity classes looking like that:

我有将近一百个实体类看起来像这样：

[Serializable]
public class SampleEntity : INotifyPropertyChanged
{
    private string name;
    public string Name
    {
        get { return this.name; }
        set { this.name = value; FirePropertyChanged("Name"); }
    }

    [field:NonSerialized]
    public event PropertyChangedEventHandler PropertyChanged;

    private void FirePropertyChanged(string propertyName)
    {
        if (this.PropertyChanged != null)
            this.PropertyChanged(this,
                new PropertyChangedEventArgs(propertyName));
    }
}

Notice the [field:NonSerialized]attribute on PropertyChanged. This is necessary as some of the observers (in my case - a grid displaying the entities for edition) may not be serializable, and the entity has to be serializable, because it is provided - via remoting - by an application running on a separater machine.

注意 上的[field:NonSerialized]属性PropertyChanged。这是必要的，因为一些观察者（在我的情况下 - 显示编辑实体的网格）可能无法序列化，并且实体必须是可序列化的，因为它是由在单独的机器上运行的应用程序通过远程处理提供的.

This solution works fine for trivial cases. However, it is possible that some of the observers are [Serializable], and would need to be preserved. How should I handle this?

此解决方案适用于琐碎的情况。但是，某些观察者可能是[Serializable]，并且需要保留。我该如何处理？

Solutions I am considering:

我正在考虑的解决方案：

• full ISerializable- custom serialization requires writing a lot of code, I'd prefer not to do this
• using [OnSerializing]and [OnDeserializing]attributes to serialize PropertyChangedmanually - but those helper methods provide only SerializationContext, which AFAIK does not store serialization data (SerializationInfodoes that)

• 完全ISerializable自定义序列化需要编写大量代码，我不想这样做
• 使用[OnSerializing]和[OnDeserializing]属性PropertyChanged手动序列化- 但这些辅助方法仅提供SerializationContextAFAIK 不存储序列化数据（SerializationInfo这样做）

采纳答案by Kent Boogaart

You're right that the first option is more work. While it can potentially give you a more efficient implementation, it will complicate your entities a lot. Consider that if you have a base Entityclass that implements ISerializable, all subclasses also have to manually implement serialization!

你是对的，第一个选择是更多的工作。虽然它可能会为您提供更有效的实现，但它会使您的实体复杂化很多。考虑一下，如果您有一个Entity实现的基类ISerializable，那么所有子类也必须手动实现序列化！

The trick to getting the second option to work, is to continue marking the event as non-serializable, but to have a second field that isserializable and that you populate yourself during the appropriate serialization hooks. Here is a sample I just wrote to show you how:

使第二个选项起作用的技巧是继续将事件标记为不可序列化，但要有一个可序列化的第二个字段，并在适当的序列化挂钩期间填充自己。这是我刚刚写的一个示例，用于向您展示如何操作：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            var entity = new Entity();
            entity.PropertyChanged += new SerializableHandler().PropertyChanged;
            entity.PropertyChanged += new NonSerializableHandler().PropertyChanged;

            Console.WriteLine("Before serialization:");
            entity.Name = "Someone";

            using (var memoryStream = new MemoryStream())
            {
                var binaryFormatter = new BinaryFormatter();
                binaryFormatter.Serialize(memoryStream, entity);
                memoryStream.Position = 0;
                entity = binaryFormatter.Deserialize(memoryStream) as Entity;
            }

            Console.WriteLine();
            Console.WriteLine("After serialization:");
            entity.Name = "Kent";

            Console.WriteLine();
            Console.WriteLine("Done - press any key");
            Console.ReadKey();
        }

        [Serializable]
        private class SerializableHandler
        {
            public void PropertyChanged(object sender, PropertyChangedEventArgs e)
            {
                Console.WriteLine("  Serializable handler called");
            }
        }

        private class NonSerializableHandler
        {
            public void PropertyChanged(object sender, PropertyChangedEventArgs e)
            {
                Console.WriteLine("  Non-serializable handler called");
            }
        }
    }

    [Serializable]
    public class Entity : INotifyPropertyChanged
    {
        private string _name;
        private readonly List<Delegate> _serializableDelegates;

        public Entity()
        {
            _serializableDelegates = new List<Delegate>();
        }

        public string Name
        {
            get { return _name; }
            set
            {
                if (_name != value)
                {
                    _name = value;
                    OnPropertyChanged("Name");
                }
            }
        }

        [field:NonSerialized]
        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnPropertyChanged(PropertyChangedEventArgs e)
        {
            var handler = PropertyChanged;

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

        protected void OnPropertyChanged(string propertyName)
        {
            OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
        }

        [OnSerializing]
        public void OnSerializing(StreamingContext context)
        {
            _serializableDelegates.Clear();
            var handler = PropertyChanged;

            if (handler != null)
            {
                foreach (var invocation in handler.GetInvocationList())
                {
                    if (invocation.Target.GetType().IsSerializable)
                    {
                        _serializableDelegates.Add(invocation);
                    }
                }
            }
        }

        [OnDeserialized]
        public void OnDeserialized(StreamingContext context)
        {
            foreach (var invocation in _serializableDelegates)
            {
                PropertyChanged += (PropertyChangedEventHandler)invocation;
            }
        }
    }
}