Json.net 上的反序列化更改属性类型和名称

使用 json.net，当我反序列化 json 字符串时，我需要将 json 列表映射到另一个字段并转换类型。

为了清楚起见，我有这个类（它是生成的代码，我无法更改它）：

[Serializable]
public partial class Nbgv
{
    public virtual IReadOnlyList<string> BuildMetadataWithCommitId => BuildMetadataWithCommitIdInternal.AsReadOnly();
    internal List<string> BuildMetadataWithCommitIdInternal { get; set; } = new List<string>();
}

我有这个 json 字符串：

string json = @"{
    ""BuildMetadataWithCommitId"": [
        ""c390a213b7""
    ]
}";

如你看到的BuildMetadataWithCommitId依赖于取决于BuildMetadataWithCommitIdInternal.

我使用自定义解析器尝试了几件事，但没有任何效果。我没有找到如何告诉 json.net 如果您找到一个通用列表的属性，请将其映射到以 *Internal 结尾的字段。

private class CustomContractResolver : DefaultContractResolver
{
    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        var property = base.CreateProperty(member, memberSerialization);
        property.Writable = true;
        if (IsList(property.PropertyType))
        {
            property.PropertyName += "Internal";
            property.PropertyType = ToList(property.PropertyType);
        }

        return property;
    }

    private Type ToList(Type t)
    {
        var genericListType = typeof(List<>);
        var specificListType = genericListType.MakeGenericType(t.GenericTypeArguments[0]);
        return specificListType;
    }

    private bool IsList(Type t)
    {
        if (t == null) return false;

        var res = t.IsGenericType &&
                   t.GetGenericTypeDefinition().IsAssignableFrom(typeof(IReadOnlyList<>));

        return res;
    }
}

你的基本问题是你的CustomContractResolver仅改变PropertyName https://www.newtonsoft.com/json/help/html/P_Newtonsoft_Json_Serialization_JsonProperty_PropertyName.htm and PropertyType https://www.newtonsoft.com/json/help/html/P_Newtonsoft_Json_Serialization_JsonProperty_PropertyType.htm归来的JsonProperty https://www.newtonsoft.com/json/help/html/T_Newtonsoft_Json_Serialization_JsonProperty.htm，然而底层的PropertyInfo https://learn.microsoft.com/en-us/dotnet/api/system.reflection.propertyinfo?view=netframework-4.8它的创造来源仍然是公共替代财产，而不是私人内部“真实”财产。就这样ValueProvider https://www.newtonsoft.com/json/help/html/P_Newtonsoft_Json_Serialization_JsonProperty_ValueProvider.htm，除其他外，仍然是错误的。

你需要做的是生成一个JsonProperty对于内部属性，更正其名称和可访问性，然后返回代替 the JsonProperty为了公共财产。这将确保序列化程序将序列化和反序列化内部属性而不是其公共代理。

以下合同解析器完成这项工作：

public class CustomContractResolver : DefaultContractResolver
{
    const string InternalSuffix = "Internal";

    protected override JsonProperty CreateProperty(MemberInfo member, MemberSerialization memberSerialization)
    {
        var property = member as PropertyInfo;
        var jProperty = base.CreateProperty(member, memberSerialization);
        if (property != null && jProperty != null && memberSerialization != MemberSerialization.Fields && !jProperty.HasMemberAttribute)
        {
            var replacementName = jProperty.UnderlyingName + InternalSuffix;

            // Check for replacement property.
            var replacementProperty = jProperty.DeclaringType.GetProperty(replacementName, BindingFlags.Instance | BindingFlags.NonPublic);
            if (replacementProperty != null
                && replacementProperty.GetGetMethod(true) != null && replacementProperty.GetSetMethod(true) != null
                && ReplacementTypeCompatible(property, replacementProperty.PropertyType)
                )
            {
                var replacementJProperty = base.CreateProperty(replacementProperty, memberSerialization);
                replacementJProperty.PropertyName = jProperty.PropertyName;
                if (!replacementJProperty.Readable && replacementProperty.GetGetMethod(true) != null)
                    replacementJProperty.Readable = true;
                if (!replacementJProperty.Writable && replacementProperty.GetSetMethod(true) != null)
                    replacementJProperty.Writable = true;
                return replacementJProperty;
            }

            // Check for replacement field.
            var replacementField = jProperty.DeclaringType.GetField(replacementName, BindingFlags.Instance | BindingFlags.NonPublic);
            if (replacementField != null
                && ReplacementTypeCompatible(property, replacementField.FieldType)
                )
            {
                var replacementJProperty = base.CreateProperty(replacementField, memberSerialization);
                replacementJProperty.PropertyName = jProperty.PropertyName;
                replacementJProperty.Readable = true;
                replacementJProperty.Writable = true;
                return replacementJProperty;
            }
        }

        return jProperty;
    }

    static bool ReplacementTypeCompatible(PropertyInfo property, Type replacementType)
    {
        // Add here whatever restrictions you need
        if (property.PropertyType.IsGenericType && typeof(IReadOnlyList<>).IsAssignableFrom(property.PropertyType.GetGenericTypeDefinition())
            && replacementType.IsGenericType && typeof(List<>).IsAssignableFrom(replacementType.GetGenericTypeDefinition())
            && replacementType.GetGenericArguments().SequenceEqual(property.PropertyType.GetGenericArguments()))
            return true;
        return false;
    }
}

要使用它，请将解析器的实例缓存在某处表现 https://www.newtonsoft.com/json/help/html/Performance.htm#ReuseContractResolver:

static IContractResolver customContractResolver = new CustomContractResolver();

并像这样反序列化：

var settings = new JsonSerializerSettings
{
    ContractResolver = customContractResolver,
};
var root = JsonConvert.DeserializeObject<Nbgv>(json, settings);

Notes:

• 在你的问题中，你说我需要将 json 列表映射到另一个field