c# - 如何强制 Newtonsoft Json 序列化所有属性？ (具有 "Specified"属性的奇怪行为)

Question

各位程序员，我在 Newtonsoft.Json 中遇到了一个奇怪的行为。

当我尝试序列化一个如下所示的对象时:

public class DMSDocWorkflowI
{
    [JsonProperty("DMSDocWorkflowIResult")]
    public bool DMSDocWorkflowIResult { get; set; }

    [JsonProperty("DMSDocWorkflowIResultSpecified")]
    public bool DMSDocWorkflowIResultSpecified { get; set; }
}

使用这个没有自定义转换器/绑定(bind)器/契约解析器的简单调用:

var testObject = new DMSDocWorkflowI();
var json = JsonConvert.SerializeObject(testObject, Formatting.Indented);

甚至使用 JToken.FromObject(...) 我总是只得到一个属性:

{
   "DMSDocWorkflowIResultSpecified": false
}

当我附加跟踪编写器时，它只捕捉到这个:

[0]: "2016-08-30T11:06:27.779 Info Started serializing *****DMSDocWorkflowI. Path ''."
[1]: "2016-08-30T11:06:27.779 Verbose IsSpecified result for property 'DMSDocWorkflowIResult' on *****DMSDocWorkflowI: False. Path ''."
[2]: "2016-08-30T11:06:27.779 Info Finished serializing *****.DMSDocWorkflowI. Path ''."
[3]: "2016-08-30T11:06:27.780 Verbose Serialized JSON: \r\n{\r\n  \"DMSDocWorkflowIResultSpecified\": false\r\n}"

因此，Newtonsoft.Json 似乎有点神奇地处理了这个“指定”属性。我可以关掉它吗？我需要这两个属性来生成具有这些名称的 JSON。

Answer 1

在 Json.NET 4.0.1 release notes 中非常提到了这种行为。 : 新功能 - 添加了 XmlSerializer 样式指定的属性支持。 XmlSerializer 功能又在 MinOccurs Attribute Binding Support 中描述。 :

[For optional fields] Xsd.exe generates a public field of type bool whose name is the element field's name with Specified appended. For example, if the element field's name is startDate, the bool field's name becomes startDateSpecified. When serializing an object to XML, the XmlSerializer class checks the value of the bool field to determine whether to write the element.

我觉得好像应该记录此功能 here ，但不是。你可能想要 open a documentation issue与 Newtonsoft 合作。

由于您不希望出现这种情况，如果您使用 Json.NET 11.0.1 or later ，您可以通过实例化自己的 DefaultContractResolver 为所有类禁用它和设置 DefaultContractResolver.IgnoreIsSpecifiedMembers = true :

public static class JsonContractResolvers
{
    // Newtonsoft recommends caching and reusing contract resolvers for best performance:
    // https://www.newtonsoft.com/json/help/html/Performance.htm#ReuseContractResolver
    // But be sure not to modify IgnoreIsSpecifiedMembers after the contract resolver is first used to generate a contract.

    public static readonly DefaultContractResolver IgnoreIsSpecifiedMembersResolver =
        new DefaultContractResolver { IgnoreIsSpecifiedMembers = true };
}

然后传递给JsonConvert如下:

var settings = new JsonSerializerSettings { ContractResolver = JsonContractResolvers.IgnoreIsSpecifiedMembersResolver };
var json = JsonConvert.SerializeObject(testObject, Formatting.Indented, settings);

或者创建一个 JToken 做:

var jToken = JToken.FromObject(testObject, JsonSerializer.CreateDefault(settings));

如果您使用的是早期版本，则需要创建并缓存 custom contract resolver :

public static class JsonContractResolvers
{
    public static readonly DefaultContractResolver IgnoreIsSpecifiedMembersResolver =
        new IgnoreSpecifiedContractResolver();
}

internal class IgnoreSpecifiedContractResolver : DefaultContractResolver
{
    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        var property = base.CreateProperty(member, memberSerialization);
        property.GetIsSpecified = null;
        property.SetIsSpecified = null;
        return property;
    }
}