定制系列化

我有一些必须序列化的对象：

class Displayable{
  string name;
  Sprite icon;
}

The icon字段需要自定义序列化，因为Sprites 已经被序列化（在不同的文件中，具有自己的格式，由游戏引擎），我只需要存储一种引用它们的方法（比方说string，是里面的钥匙Dictionary<string, Sprite>).

Using BinaryFormatter我尝试实施ISerializable and ISerializationSurrogate但这两种方法都会在反序列化时创建 Sprite 对象的新实例，因此它们不适合我的情况。我想要具有相同的功能ISerializationSurrogate除非我不想要第一个参数SetObjectData(object obj, SerializationInfo info, StreamingContext context, ISurrogateSelector selector)因为我需要返回内存中已有的对象，而不是从反序列化器接收新实例并用数据填充它。

我还尝试了像 SharpSerializer 这样的外部库，但我不喜欢公共无参数构造函数的限制，而且它并不能真正让您自定义特殊类的序列化。 我读过有关 ProtoBuffers 的内容，但它不支持继承，我需要在其他地方使用它。

所以我的要求是：

• 继承支持
• 能够为某些类型定义自定义序列化
• 这些自定义类型的反序列化不应自行创建实例

有图书馆这样做吗？

不然我是不是太挑剔了？通常如何实现对存储在其他地方的对象的引用的序列化？

先感谢您。

编辑： 这就是我想要的

public class SerializableSprite : ISerializationSurrogate
{
  public static Dictionary<string, Sprite> sprites;
  public void GetObjectData(object obj, SerializationInfo info, StreamingContext context) {
    Sprite sprite = obj as Sprite;
    info.AddValue("spriteKey", sprite.name);
  }
  // The first parameter in this function is a newly instantiated Sprite, which I don't need
  public object SetObjectData(object obj, SerializationInfo info, StreamingContext context, ISurrogateSelector selector) {
    return sprites[info.GetString("spriteKey")];
  }
}

为了阻止BinaryFormatter从创建一个新实例Sprite在反序列化期间，在序列化你可以打电话SerializationInfo.SetType(Type)指定要插入到序列化流中的备用类型信息（通常是某种代理类型）。反序列化期间SetObjectData()将传递代理实例而不是“真实”类型来初始化。该代理类型必须依次实现IObjectReference这样“真实”对象最终可以插入到对象图中，特别是通过在精灵表中查找它。

以下代码执行此操作：

class ObjectReferenceProxy<T> : IObjectReference
{
    public T RealObject { get; set; }

    #region IObjectReference Members

    object IObjectReference.GetRealObject(StreamingContext context)
    {
        return RealObject;
    }

    #endregion
}

public sealed class SpriteSurrogate : ObjectLookupSurrogate<string, Sprite>
{
    static Dictionary<string, Sprite> sprites = new Dictionary<string, Sprite>();
    static Dictionary<Sprite, string> spriteNames = new Dictionary<Sprite, string>();

    public static void AddSprite(string name, Sprite sprite)
    {
        if (name == null || sprite == null)
            throw new ArgumentNullException();
        sprites.Add(name, sprite);
        spriteNames.Add(sprite, name);
    }

    public static IEnumerable<Sprite> Sprites
    {
        get
        {
            return sprites.Values;
        }
    }

    protected override string GetId(Sprite realObject)
    {
        if (realObject == null)
            return null;
        return spriteNames[realObject];
    }

    protected override Sprite GetRealObject(string id)
    {
        if (id == null)
            return null;
        return sprites[id];
    }
}

public abstract class ObjectLookupSurrogate<TId, TRealObject> : ISerializationSurrogate where TRealObject : class
{
    public void Register(SurrogateSelector selector)
    {
        foreach (var type in Types)
            selector.AddSurrogate(type, new StreamingContext(StreamingContextStates.All), this);
    }

    IEnumerable<Type> Types
    {
        get
        {
            yield return typeof(TRealObject);
            yield return typeof(ObjectReferenceProxy<TRealObject>);
        }
    }

    protected abstract TId GetId(TRealObject realObject);

    protected abstract TRealObject GetRealObject(TId id);

    #region ISerializationSurrogate Members

    public void GetObjectData(object obj, SerializationInfo info, StreamingContext context)
    {
        var original = (TRealObject)obj;
        var id = GetId(original);
        info.AddValue("id", id);
        // use Info.SetType() to force the serializer to construct an object of type ObjectReferenceWrapper<TRealObject> during deserialization.
        info.SetType(typeof(ObjectReferenceProxy<TRealObject>));
    }

    public object SetObjectData(object obj, SerializationInfo info, StreamingContext context, ISurrogateSelector selector)
    {
        // Having constructed an object of type ObjectReferenceWrapper<TRealObject>, 
        // look up the real sprite using the id in the serialization stream.
        var wrapper = (ObjectReferenceProxy<TRealObject>)obj;
        var id = (TId)info.GetValue("id", typeof(TId));
        wrapper.RealObject = GetRealObject(id);
        return wrapper;
    }

    #endregion
}

然后将其应用到BinaryFormatter如下：

        var selector = new SurrogateSelector();
        var spriteSurrogate = new SpriteSurrogate();
        spriteSurrogate.Register(selector);

        BinaryFormatter binaryFormatter = new BinaryFormatter(selector, new StreamingContext());

Sample fiddle.

Update

虽然上面的代码可以在 .Net 3.5 及更高版本中运行，但它显然不能在unity3d尽管由于一些问题而编译成功IObjectReference。以下也适用于 .Net 3.5 及更高版本，并且还避免使用IObjectReference通过返回真实对象ISerializationSurrogate.SetObjectData()。因此它也应该在 unity3d 中工作（在评论中确认）：

public sealed class SpriteSurrogate : ObjectLookupSurrogate<string, Sprite>
{
    static Dictionary<string, Sprite> sprites = new Dictionary<string, Sprite>();
    static Dictionary<Sprite, string> spriteNames = new Dictionary<Sprite, string>();

    public static void AddSprite(string name, Sprite sprite)
    {
        if (name == null || sprite == null)
            throw new ArgumentNullException();
        sprites.Add(name, sprite);
        spriteNames.Add(sprite, name);
    }

    public static IEnumerable<Sprite> Sprites
    {
        get
        {
            return sprites.Values;
        }
    }

    protected override string GetId(Sprite realObject)
    {
        if (realObject == null)
            return null;
        return spriteNames[realObject];
    }

    protected override Sprite GetRealObject(string id)
    {
        if (id == null)
            return null;
        return sprites[id];
    }
}

public abstract class ObjectLookupSurrogate<TId, TRealObject> : ISerializationSurrogate where TRealObject : class
{
    class SurrogatePlaceholder
    {
    }

    public void Register(SurrogateSelector selector)
    {
        foreach (var type in Types)
            selector.AddSurrogate(type, new StreamingContext(StreamingContextStates.All), this);
    }

    IEnumerable<Type> Types
    {
        get
        {
            yield return typeof(TRealObject);
            yield return typeof(SurrogatePlaceholder);
        }
    }

    protected abstract TId GetId(TRealObject realObject);

    protected abstract TRealObject GetRealObject(TId id);

    #region ISerializationSurrogate Members

    public void GetObjectData(object obj, SerializationInfo info, StreamingContext context)
    {
        var original = (TRealObject)obj;
        var id = GetId(original);
        info.AddValue("id", id);
        // use Info.SetType() to force the serializer to construct an object of type SurrogatePlaceholder during deserialization.
        info.SetType(typeof(SurrogatePlaceholder));
    }

    public object SetObjectData(object obj, SerializationInfo info, StreamingContext context, ISurrogateSelector selector)
    {
        // Having constructed an object of type SurrogatePlaceholder, 
        // look up the real sprite using the id in the serialization stream.
        var id = (TId)info.GetValue("id", typeof(TId));
        return GetRealObject(id);
    }

    #endregion
}

Sample 小提琴#2.