如何使 Json 序列化忽略字典键

Question

我正在尝试序列化一个类中的字典，即使我将 ProcessDictionaryKeys 参数设置为 false，CustomAttributes 字典中的键也会被格式化。

我已经添加了[JsonProperty]，如下图：

[JsonProperty(NamingStrategyType = typeof(SnakeCaseNamingStrategy), NamingStrategyParameters = new object[] { false, false })]
public IDictionary<string, string> CustomAttributes { get; set; }

我的 CustomAttributes 数据如下所示：

CustomAttributes = new Dictionary<string, string>()
{
    {"Custom Attribute 1", "1"},
    {"CustomAttribute 2", "2"}
}

生成的 JSON 如下所示：

custom_attributes\":{\"custom Attribute 1\":\"1\",\"customAttribute 2\":\"2\"

如您所见，每个字典键的第一个字母都没有大写。我怎样才能阻止这种情况发生？

编辑：将 ProcessDictionaryKeys 参数更改为 true 似乎没有任何区别。

Answer 1

如演示小提琴 #1 here 中所示，仅使用问题中的代码不会重现问题。

相反，您必须使用JsonSerializerSettings.ContractResolver.NamingStrategy.ProcessDictionaryKeys = true 的一些全局序列化程序设置进行序列化，例如CamelCasePropertyNamesContractResolver：

var settings = new JsonSerializerSettings
{
    ContractResolver = new CamelCasePropertyNamesContractResolver(),
};
var json = JsonConvert.SerializeObject(root, Formatting.Indented, settings);

演示小提琴 #2 here.

假设这是正确的，[JsonProperty(NamingStrategyType = typeof(SnakeCaseNamingStrategy), NamingStrategyParameters = new object[] { false, false })] 不会导致字典键被逐字序列化的原因是 JsonPropertyAttribute.NamingStrategyType 仅适用于 属性名称本身（此处为 CustomAttributes）而不是属性的项目的属性名称。如果您想对属性的项目应用命名策略，您需要类似 ItemNamingStrategyType 的东西——但 JsonPropertyAttribute 没有这样的功能。

那么，你有什么选择？

1. 您可以修改全局命名策略以逐字序列化字典名称，如 Keep casing when serializing dictionaries 所示。

2. 您可以将Dictionary<TKey, TValue> 子类化并将[JsonDictionary(NamingStrategyType = typeof(DefaultNamingStrategy))] 应用于它，如this answer 中所示Applying JsonDictionary attribute to dictionary：

   [JsonDictionary(NamingStrategyType = typeof(DefaultNamingStrategy))]
   public class VerbatimDictionary<TKey, TValue> : Dictionary<TKey, TValue>
   {
   }
   

   然后：

   CustomAttributes = new VerbatimDictionary<string, string>()
   {
       {"Custom Attribute 1", "1"},
       {"CustomAttribute 2", "2"}
   }
   

   演示小提琴#3 here.

3. 您可以引入一个custom JsonConverter，它使用默认命名策略序列化一个IDictionary<TKey, TValue>。首先，定义如下转换器：

   public class VerbatimDictionaryConverter<TKey, TValue> : JsonConverter<IDictionary<TKey, TValue>>
   {
       [JsonDictionary(NamingStrategyType = typeof(DefaultNamingStrategy))]
       class VerbatimDictionarySerializationSurrogate : IReadOnlyDictionary<TKey, TValue>
       {
           readonly IDictionary<TKey, TValue> dictionary;
   
           public VerbatimDictionarySerializationSurrogate(IDictionary<TKey, TValue> dictionary) 
           { 
               if (dictionary == null) 
                   throw new ArgumentNullException(nameof(dictionary));
               this.dictionary = dictionary; 
           }
           public bool ContainsKey(TKey key) { return dictionary.ContainsKey(key); }
           public bool TryGetValue(TKey key, out TValue value) { return dictionary.TryGetValue(key, out value); }
           public TValue this[TKey key] { get { return dictionary[key]; } }
           public IEnumerable<TKey> Keys { get { return dictionary.Keys; } }
           public IEnumerable<TValue> Values { get { return dictionary.Values; } }
           public int Count { get { return dictionary.Count; } }
           public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator() { return dictionary.GetEnumerator(); }
           IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); }
       }
   
       public override void WriteJson(JsonWriter writer, IDictionary<TKey, TValue> value, JsonSerializer serializer)
       {
           serializer.Serialize(writer, new VerbatimDictionarySerializationSurrogate(value));
       }
   
       public override bool CanRead { get { return false; } }
   
       public override IDictionary<TKey, TValue> ReadJson(JsonReader reader, Type objectType, IDictionary<TKey, TValue> existingValue, bool hasExistingValue, JsonSerializer serializer) { throw new NotImplementedException(); }
   }
   

   并应用如下：

   [JsonConverter(typeof(VerbatimDictionaryConverter<string, string>))]
   public IDictionary<string, string> CustomAttributes { get; set; }       
   

   演示小提琴 #4 here.