Json.Net无法序列化从字典派生的类的属性

Question

我有一个派生自Dictionary的类。类本身也有一个ClientId属性。我想用Json.Net将这个类的集合反序列化为JSON字符串所以按照这里的文档

public interface IClientSettings: IDictionary<string, string>
{        
    string ClientId { get; set; }        
}
public class ClientSettings : Dictionary<string, string>, IClientSettings
{        
    public string ClientId { get; set; }
}

然后我将list反序列化为字符串

        var list = new List<IClientSettings>();
        var client1 = new ClientSettings();
        client1.ClientId = "Client1";
        client1.Add("key1", "value1");
        client1.Add("key2", "value2");
        client1.Add("key3", "value3");
        var client2 = new ClientSettings();
        client1.ClientId = "Client2";
        client2.Add("key1", "value1");
        client2.Add("key2", "value2");
        client2.Add("key3", "value3");
        list.Add(client1);
        list.Add(client2);
        string json = JsonConvert.SerializeObject(list, Formatting.Indented);
        Console.WriteLine(json);

然而，这并不序列化Clientid属性。输出如下:

[
  {
    "key1": "value1",
    "key2": "value2",
    "key3": "value3"
  },
  {
    "key1": "value1",
    "key2": "value2",
    "key3": "value3"
  }
]

我不知道我在这里错过了什么。我也发现这里的建议，建议做自定义序列化，这是我唯一的选择吗?

Answer 1

是的，您是正确的，您将需要执行某种自定义序列化。Json。NET将把字典的键/值对序列化为JSON对象(使用JsonDictionaryContract)，或者如果用[JsonObject]标记类型，则将字典的属性序列化为JSON对象(使用JsonObjectContract) -但不是两者都序列化。我怀疑两者都没有实现，从而避免当字典包含与属性同名的键时运行时名称冲突的可能性，例如:

var client3 = new ClientSettings();
client3.ClientId = "Client1";
client3["ClientId"] = "Conflicting Value";

根据IETF标准，

当一个对象中的名称不是唯一的，接收到这样一个对象的软件的行为是不可预测的。

因此，这种情况最好避免。

一种可能的实现如下:

[JsonObject(MemberSerialization = MemberSerialization.OptIn)]
public class ClientSettings : Dictionary<string, string>, IClientSettings
{
    [JsonProperty]
    public string ClientId { get; set; }
    [JsonProperty]
    IDictionary<string, string> Items { get { return new DictionaryWrapper<string, string>(this); } }
}

使用

public class DictionaryWrapper<TKey, TValue> : IDictionary<TKey, TValue>
{
    readonly IDictionary<TKey, TValue> dictionary;
    public DictionaryWrapper(IDictionary<TKey, TValue> dictionary)
    {
        if (dictionary == null)
            throw new ArgumentNullException("dictionary");
        this.dictionary = dictionary;
    }
    #region IDictionary<TKey,TValue> Members
    public void Add(TKey key, TValue value) { dictionary.Add(key, value); }
    public bool ContainsKey(TKey key) { return dictionary.ContainsKey(key); }
    public ICollection<TKey> Keys { get { return dictionary.Keys; } }
    public bool Remove(TKey key) { return dictionary.Remove(key); }
    public bool TryGetValue(TKey key, out TValue value) { return dictionary.TryGetValue(key, out value); }
    public ICollection<TValue> Values { get { return dictionary.Values; } }
    public TValue this[TKey key]
    {
        get { return dictionary[key]; }
        set { dictionary[key] = value; }
    }
    #endregion
    #region ICollection<KeyValuePair<TKey,TValue>> Members
    public void Add(KeyValuePair<TKey, TValue> item) { dictionary.Add(item); }
    public void Clear() { dictionary.Clear(); }
    public bool Contains(KeyValuePair<TKey, TValue> item) { return dictionary.Contains(item); }
    public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex) { dictionary.CopyTo(array, arrayIndex); }
    public int Count { get { return dictionary.Count; } }
    public bool IsReadOnly { get { return dictionary.IsReadOnly; } }
    public bool Remove(KeyValuePair<TKey, TValue> item) { return dictionary.Remove(item); }
    #endregion
    #region IEnumerable<KeyValuePair<TKey,TValue>> Members
    public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator() { return dictionary.GetEnumerator(); }
    #endregion
    #region IEnumerable Members
    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return GetEnumerator(); }
    #endregion
}

MemberSerialization.OptIn用于防止基类属性(如Count、Comparer、Keys和Values)被序列化。

这样，您的JSON将看起来像:

[
  {
    "ClientId": "Client2",
    "Items": {
      "key1": "value1",
      "key2": "value2",
      "key3": "value3"
    }
  }
]