c# - 使用附加属性序列化自定义集合并添加到连接项 propertyChanged 事件

Question

我有一个自定义集合，我想用 JSON.NET 对其进行序列化:

我需要它来序列化此自定义集合中的子集合。

在反序列化时，我需要为集合中的项目连接 PropertyChanged 事件。

如果我按原样传递我的集合，Json 会看到 IEnumerable 并正确序列化集合中的项目，但会忽略其中的其他集合。

如果我使用 [JsonObject] 属性集合，它将序列化所有内部集合，但不序列化内部 _list；

如果我将 [JsonProperty] 添加到内部 _list，它将序列化所有集合。

但由于它在反序列化期间将 _list 设置为属性，因此不会调用我的自定义集合的 Add 方法，因此 _list 中的项目的 propertyChanged 事件永远不会被连接。

我尝试隐藏内部 _list 并用公共(public) getter setter 包装它，我想如果在反序列化期间它使用公共(public) setter 来设置内部 _list 我可以附加到那里的项目事件，但这也不起作用。

在反序列化过程中，我可以做些什么来连接内部 _list 中项目的 notifyproperty changed 事件？

编辑:我尝试了一个转换器:

public class TrackableCollectionConverter : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return objectType == typeof(TrackableCollectionCollection<ITrackableEntity>);
    }

    public override object ReadJson(
        JsonReader reader, Type objectType,
        object existingValue, JsonSerializer serializer)
    {
        // N.B. null handling is missing
        var surrogate = serializer.Deserialize<TrackableCollectionCollection<ITrackableEntity>>(reader);


        var trackableCollection = new TrackableCollectionCollection<ITrackableEntity>();
        foreach (var el in surrogate)
            trackableCollection.Add(el);

        foreach (var el in surrogate.NewItems)
            trackableCollection.NewItems.Add(el);

        foreach (var el in surrogate.ModifiedItems)
            trackableCollection.ModifiedItems.Add(el);

        foreach (var el in surrogate.DeletedItems)
            trackableCollection.DeletedItems.Add(el);

        return trackableCollection;
    }

    public override void WriteJson(JsonWriter writer, object value,
                                   JsonSerializer serializer)
    {
        serializer.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
        serializer.Serialize(writer, value);
    }

}

给出错误:

{"Message":"An error has occurred.","ExceptionMessage":"The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; charset=utf-8'.","ExceptionType":"System.InvalidOperationException","StackTrace":null,"InnerException":{"Message":"An error has occurred.","ExceptionMessage":"Token PropertyName in state Property would result in an invalid JSON object. Path '[0]'.","ExceptionType":"Newtonsoft.Json.JsonWriterException","StackTrace":" at Newtonsoft.Json.JsonWriter.AutoComplete(JsonToken tokenBeingWritten)\r\n at Newtonsoft.Json.JsonWriter.InternalWritePropertyName(String name)\r\n at Newtonsoft.Json.JsonTextWriter.WritePropertyName(String name, Boolean escape)\r\n at Newtonsoft.Json.Serialization.JsonProperty.WritePropertyName(JsonWriter writer)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject(JsonWriter writer, Object value, JsonObjectContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeList(JsonWriter writer, IEnumerable values, JsonArrayContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n at Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value, Type objectType)\r\n at Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value, Type objectType)\r\n at Newtonsoft.Json.JsonSerializer.Serialize(JsonWriter jsonWriter, Object value)\r\n at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n at System.Net.Http.Formatting.JsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, HttpContent content)\r\n at System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStreamAsync(Type type, Object value, Stream writeStream, HttpContent content, TransportContext transportContext, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n at System.Runtime.CompilerServices.TaskAwaiter.GetResult()\r\n at System.Web.Http.WebHost.HttpControllerHandler.d__1b.MoveNext()"}}

这是我到目前为止的收藏。

[Serializable]
[JsonObject]
[JsonConverter(typeof(TrackableCollectionConverter))]
public class TrackableCollectionCollection<T> : IList<T> where T : ITrackableEntity
{
    [JsonIgnore]
    IList<T> _list = new List<T>();

    [JsonProperty]
    public IList<T> List
    {
        get { return _list; }
        set 
        { 
            _list = value; 

            foreach(var item in _list)
                item.PropertyChanged += item_PropertyChanged;
        }
    } 

    [DataMember]
    public IList<T> NewItems
    {
        get { return _newItems; }
    }
    IList<T> _newItems = new List<T>();

    [DataMember]
    public IList<T> ModifiedItems
    {
        get { return _modifiedChildren; }
    }
    IList<T> _modifiedChildren = new List<T>();

    [DataMember]
    public IList<T> DeletedItems
    {
        get { return _deletedItems; }
    }
    IList<T> _deletedItems = new List<T>();

    #region Implementation of IEnumerable

    public IEnumerator<T> GetEnumerator()
    {
        return _list.GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }

    #endregion

    #region Implementation of ICollection<T>

    public void Add(T item)
    {
        if (item.Id.Equals(default(Guid)))
            _newItems.Add(item);
        else
        {
            // I thought about doing this but that would screw the EF object generation.
            // throw new NotSupportedException("");
        }

        item.PropertyChanged += item_PropertyChanged;

        _list.Add(item);
    }


    public void Clear()
    {
        NewItems.Clear();
        ModifiedItems.Clear();

        foreach(var item in _list)
        {
            item.PropertyChanged -= item_PropertyChanged;
            DeletedItems.Add(item);
        }

        _list.Clear();
    }

    public bool Contains(T item)
    {
        return _list.Contains(item);
    }

    public void CopyTo(T[] array, int arrayIndex)
    {
        _list.CopyTo(array, arrayIndex);
    }

    public bool Remove(T item)
    {
        if (NewItems.Contains(item))
            NewItems.Remove(item);

        if (ModifiedItems.Contains(item))
            ModifiedItems.Remove(item);

        if (!DeletedItems.Contains(item))
            DeletedItems.Add(item);

        return _list.Remove(item);
    }

    public int Count
    {
        get { return _list.Count; }
    }

    public bool IsReadOnly
    {
        get { return _list.IsReadOnly; }
    }

    #endregion

    #region Implementation of IList<T>

    public int IndexOf(T item)
    {
        return _list.IndexOf(item);
    }

    public void Insert(int index, T item)
    {
        if (item.Id.Equals(default(Guid)))
            _newItems.Add(item);
        else
        {
            // I thought about doing this but that would screw the EF object generation.
            // throw new NotSupportedException("");
        }

        item.PropertyChanged += item_PropertyChanged;

        _list.Insert(index, item);
    }

    public void RemoveAt(int index)
    {
        var item = this[index];

        if (NewItems.Contains(item))
            NewItems.Remove(item);

        if (ModifiedItems.Contains(item))
            ModifiedItems.Remove(item);

        if (!DeletedItems.Contains(item))
            DeletedItems.Add(item);

        _list.RemoveAt(index);
    }

    public T this[int index]
    {
        get { return _list[index]; }
        set { _list[index] = value; }
    }
    #endregion
    void item_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
    {
        if (((T)sender).Id.Equals(default(Guid)))
            return; // The Item is already in the newItems collection

        if (ModifiedItems.Contains((T)sender))
            return;

        ModifiedItems.Add((T)sender);

    }
}

Answer 1

您可以将自定义容器序列化为 JsonObject ，就像您现在所做的那样，并将嵌入列表序列化为代理 ObservableCollection<T> .然后您可以监听代理的添加和删除并相应地处理它们。注意——不需要自定义 JsonConverter。因为我没有你对 ITrackableEntity 的定义，这是一个快速原型(prototype)包装器 IList<T>对于 List<T> :

[Serializable]
[JsonObject]
public class ListContainer<T> : IList<T> 
{
    [JsonIgnore]
    readonly List<T> _list = new List<T>();

    [JsonProperty("List")]
    private IList<T> SerializableList
    {
        get
        {
            var proxy = new ObservableCollection<T>(_list);
            proxy.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(proxy_CollectionChanged);
            return proxy;
        }
        set
        {
            _list.Clear();
            _list.AddRange(value);
        }
    }

    void proxy_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
    {
        if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add)
        {
            foreach (var item in e.NewItems.Cast<T>())
                Add(item);
        }
        else if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Remove)
        {
            foreach (var item in e.NewItems.Cast<T>())
                Remove(item);
        }
        else
        {
            Debug.Assert(false);
            throw new NotImplementedException();
        }
    }

    [JsonIgnore]
    public int Count
    {
        get { return _list.Count; }
    }

    [JsonIgnore]
    public bool IsReadOnly
    {
        get { return ((IList<T>)_list).IsReadOnly; }
    }

    // Everything beyond here is boilerplate.

    #region IList<T> Members

    public int IndexOf(T item)
    {
        return _list.IndexOf(item);
    }

    public void Insert(int index, T item)
    {
        _list.Insert(index, item);
    }

    public void RemoveAt(int index)
    {
        _list.RemoveAt(index);
    }

    public T this[int index]
    {
        get
        {
            return _list[index];
        }
        set
        {
            _list[index] = value;
        }
    }

    #endregion

    #region ICollection<T> Members

    public void Add(T item)
    {
        _list.Add(item);
    }

    public void Clear()
    {
        _list.Clear();
    }

    public bool Contains(T item)
    {
        return _list.Contains(item);
    }

    public void CopyTo(T[] array, int arrayIndex)
    {
        _list.CopyTo(array, arrayIndex);
    }

    public bool Remove(T item)
    {
        return _list.Remove(item);
    }

    #endregion

    #region IEnumerable<T> Members

    public IEnumerator<T> GetEnumerator()
    {
        return _list.GetEnumerator();
    }

    #endregion

    #region IEnumerable Members

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }

    #endregion
}

然后，进行测试:

    public static void TestListContainerJson()
    {
        var list = new ListContainer<int>();
        list.Add(101);
        list.Add(102);
        list.Add(103);

        var json = JsonConvert.SerializeObject(list);
        var newList = JsonConvert.DeserializeObject<ListContainer<int>>(json);
        Debug.Assert(list.SequenceEqual(newList)); // No assert.
    }

更新

事实证明，Json.NET 遵循与 XmlSerializer 相同的模式: 如果您将代理列表序列化为一个数组，setter 将在读取后使用完全填充的数组调用，您可以根据需要添加它们:

[Serializable]
[JsonObject]
public class ListContainer<T> : IList<T>
{
    [JsonIgnore]
    readonly List<T> _list = new List<T>();

    [JsonProperty("List")]
    private T [] SerializableList
    {
        get
        {
            return _list.ToArray();
        }
        set
        {
            Clear();
            foreach (var item in value)
                Add(item);
        }
    }

    [JsonIgnore]
    public int Count
    {
        get { return _list.Count; }
    }

    [JsonIgnore]
    public bool IsReadOnly
    {
        get { return ((IList<T>)_list).IsReadOnly; }
    }

    // Everything beyond here is boilerplate.
}

这比我的第一个解决方案要干净得多。

另外，我怀疑你的 NewItems和 ModifiedItems列表包含对主要项目的引用 _list .默认情况下，Json.NET 将在序列化和反序列化期间有效地克隆这些。为避免这种情况，请查看 PreserveReferencesHandling 功能。更多 here .