如何在 Json.NET 中使用 JsonSerializerSettings 在属性中指定时禁用 TypeNameHandling？

有时我需要抑制输出"$type"即使由 Json.NET 指定属性JsonPropertyAttribute.ItemTypeNameHandling https://www.newtonsoft.com/json/help/html/P_Newtonsoft_Json_JsonPropertyAttribute_ItemTypeNameHandling.htm。如何才能做到这一点？

我的根类如下所示：

public class DomainResource
{
    [JsonProperty(ItemTypeNameHandling = TypeNameHandling.Auto)]
    public List<Extension> Extensions { get; set; }
}

另外我还有一个类层次结构Extension例如以下内容：

public class Extension
{
    readonly string url;

    public string Url { get { return url; } }

    public Extension(string url)
    {
        this.url = url;
    }
}

public class IntegerExtension : Extension
{
    public IntegerExtension(string url) : base(url) { }

    [JsonProperty("ValueInteger")]
    public int Value { get; set; }
}

我想忽略ItemTypeNameHandling在序列化过程中的某些情况下，但我无法找到一种方法来做到这一点。 当我不想要时，我尝试使用 TypeNameHandling.None 设置 JsonSerializerSettings 作为 jsonconvert 的输入"$type"使用以下代码的属性：

public static string SerializeObject(object value)
{
    JsonSerializerSettings jsonSettings = new JsonSerializerSettings
    {
        ContractResolver = new CamelCasePropertyNamesContractResolver(),
        NullValueHandling = NullValueHandling.Ignore,
        TypeNameHandling = TypeNameHandling.None,

    };
    jsonSettings.Converters.Add(new StringEnumConverter
    {
        CamelCaseText = true
    });
    return JsonConvert.SerializeObject(value, Formatting.None, jsonSettings);
}

然后使用它如下：

var res = new DomainResource();
res.Extensions = new List<Extension>();
res.Extensions.Add(new IntegerExtension("ewwer"){Value = 3});

var x = CustomJsonConvert.SerializeObject(res);

我想要的 JSON 是：

{"extensions":[{"valueInteger":3,"url":"ewwer"}]}

但它包含"$type"属性如下图：

{“扩展”：[{“$ type”：“DicomtoJsonConverter.IntegerExtension， DicomtoJsonConverter","valueInteger":3,"url":"ewwer"}]}

我怎样才能抑制输出"$type"特性不改变DomainResource class?

您可以使用custom ContractResolver https://www.newtonsoft.com/json/help/html/contractresolver.htm#CustomIContractResolverExamples即使由指定也抑制类型信息的输出JsonPropertyAttribute.TypeNameHandling https://www.newtonsoft.com/json/help/html/P_Newtonsoft_Json_JsonPropertyAttribute_TypeNameHandling.htm, JsonPropertyAttribute.ItemTypeNameHandling https://www.newtonsoft.com/json/help/html/P_Newtonsoft_Json_JsonPropertyAttribute_ItemTypeNameHandling.htm or JsonContainerAttribute.ItemTypeNameHandling https://www.newtonsoft.com/json/help/html/P_Newtonsoft_Json_JsonContainerAttribute_ItemTypeNameHandling.htm。首先，定义以下合约解析器：

public class NoTypeNameHandlingContractResolver : DefaultContractResolver
{
    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        var property = base.CreateProperty(member, memberSerialization);
        // Suppress JsonPropertyAttribute.TypeNameHandling
        property.TypeNameHandling = null;
        // Suppress JsonPropertyAttribute.ItemTypeNameHandling
        property.ItemTypeNameHandling = null;
        return property;
    }

    protected override JsonContract CreateContract(Type objectType)
    {
        var contract = base.CreateContract(objectType);
        if (contract is JsonContainerContract)
        {
            // Suppress JsonContainerAttribute.ItemTypeNameHandling
            ((JsonContainerContract)contract).ItemTypeNameHandling = null;
        }
        return contract;
    }
}

然后，修改CustomJsonConvert.SerializeObject()如下：

public static class CustomJsonConvert
{
    // You may want to cache the contract resolver for best performance, see
    // https://stackoverflow.com/questions/33557737/does-json-net-cache-types-serialization-information
    static readonly JsonSerializerSettings jsonSettings;
    static CustomJsonConvert()
    {
        jsonSettings = new JsonSerializerSettings
        {
            ContractResolver = new NoTypeNameHandlingContractResolver
            {
                NamingStrategy = new CamelCaseNamingStrategy
                {
                    // These are the settings used by CamelCasePropertyNamesContractResolver by default.
                    // Change them if this is not what you want.
                    OverrideSpecifiedNames = true,
                    ProcessDictionaryKeys = true,
                },
            },
            NullValueHandling = NullValueHandling.Ignore,
            TypeNameHandling = TypeNameHandling.None,
            Converters = { new StringEnumConverter { CamelCaseText = true } },
        };
    }

    public static string SerializeObject(object value)
    {
        return JsonConvert.SerializeObject(value, Formatting.None, jsonSettings);
    }
}

如果您使用的 Json.NET 版本早于9.0.1 https://github.com/JamesNK/Newtonsoft.Json/releases/tag/9.0.1你需要子类化CamelCasePropertyNamesContractResolver而不是子类化DefaultContractResolver since NamingStrategy https://www.newtonsoft.com/json/help/html/T_Newtonsoft_Json_Serialization_NamingStrategy.htm是在该版本中引入的。