可否扩展Newtonsoft.Json的JsonProperty特性新增自定义序列化属性？

原生JsonPropertyAttribute是密封类，无法直接继承扩展新增自定义属性，但可以通过「自定义多场景名称特性+对应场景合约解析器」的方案实现你要的多场景序列化字段名需求，完全可以达到你期望的使用效果。

步骤1：自定义多场景序列化名称特性 #

[AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
public class JsonMultiSceneNameAttribute : Attribute
{
    // Solver场景对应序列化字段名
    public string SolverPropertyName { get; set; }
    // API场景对应序列化字段名
    public string APIPropertyName { get; set; }
    // 后续新增场景只需在此处加对应属性即可
}

步骤2：实现不同场景的定制合约解析器 #

Solver场景解析器 #

序列化时优先使用标记的SolverPropertyName作为字段名：

public class SolverSceneContractResolver : DefaultContractResolver
{
    protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
    {
        var properties = base.CreateProperties(type, memberSerialization);
        foreach (var prop in properties)
        {
            // 获取属性上标记的自定义多场景特性
            var multiNameAttr = prop.AttributeProvider
                .GetAttributes(typeof(JsonMultiSceneNameAttribute), false)
                .Cast<JsonMultiSceneNameAttribute>()
                .FirstOrDefault();
            
            if (multiNameAttr != null && !string.IsNullOrWhiteSpace(multiNameAttr.SolverPropertyName))
            {
                prop.PropertyName = multiNameAttr.SolverPropertyName;
            }
        }
        return properties;
    }
}

API场景解析器 #

序列化时优先使用标记的APIPropertyName作为字段名：

public class APISceneContractResolver : DefaultContractResolver
{
    protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
    {
        var properties = base.CreateProperties(type, memberSerialization);
        foreach (var prop in properties)
        {
            var multiNameAttr = prop.AttributeProvider
                .GetAttributes(typeof(JsonMultiSceneNameAttribute), false)
                .Cast<JsonMultiSceneNameAttribute>()
                .FirstOrDefault();
            
            if (multiNameAttr != null && !string.IsNullOrWhiteSpace(multiNameAttr.APIPropertyName))
            {
                prop.PropertyName = multiNameAttr.APIPropertyName;
            }
        }
        return properties;
    }
}

SmartModel存储场景解析器 #

直接使用原生属性名作为序列化字段名：

public class SmartModelStorageContractResolver : DefaultContractResolver
{
    protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
    {
        var properties = base.CreateProperties(type, memberSerialization);
        foreach (var prop in properties)
        {
            prop.PropertyName = prop.UnderlyingName;
        }
        return properties;
    }
}

步骤3：给模型类标记特性 #

和你期望的写法几乎一致，只是特性名换成自定义的即可：

class Pipe
{
    [JsonMultiSceneName(
        SolverPropertyName = "z_axis_dimension", 
        APIPropertyName = "distance")]
    public double Length { get; set; }

    [JsonMultiSceneName(
        SolverPropertyName = "cross_sectional_dimension", 
        APIPropertyName = "diameter")]
    public double Diameter { get; set; }
}

步骤4：不同场景序列化调用示例 #

var pipe = new Pipe
{
    Length = 10.2,
    Diameter = 5.5
};

// 序列化得到SolverDTO
var solverSettings = new JsonSerializerSettings
{
    Formatting = Formatting.Indented,
    ContractResolver = new SolverSceneContractResolver()
};
string solverJson = JsonConvert.SerializeObject(pipe, solverSettings);

// 序列化得到API用DTO
var apiSettings = new JsonSerializerSettings
{
    Formatting = Formatting.Indented,
    ContractResolver = new APISceneContractResolver()
};
string apiJson = JsonConvert.SerializeObject(pipe, apiSettings);

// 序列化得到存储用SmartModelDTO
var storageSettings = new JsonSerializerSettings
{
    Formatting = Formatting.Indented,
    ContractResolver = new SmartModelStorageContractResolver()
};
string storageJson = JsonConvert.SerializeObject(pipe, storageSettings);

补充说明 #

该方案比修改/扩展原生JsonProperty的灵活性更高，后续新增其他序列化场景时，仅需做两处修改：

1. 在JsonMultiSceneNameAttribute中新增对应场景的名称属性
2. 新增对应场景的合约解析器即可，无需调整已有模型的标记逻辑

内容的提问来源于stack exchange，提问作者Francois Louw