.net - 使用 Newtonsoft.Json，如何将 JSON 反序列化为具有包含接口(interface)类型的 IEnumerable 属性的类型？

Question

我正在使用发送 JSON 的 RESTful Web 服务，我尝试使用 HttpContent.ReadAsAsync<T> 对其进行反序列化.我尝试反序列化的类型声明了一个属性，该属性返回一个包含接口(interface)类型的 IEnumerable。此代码片段演示了我尝试反序列化为的类型:

public class Data
{
    public IEnumerable<IChild> Children { get; set; };
}

问题在于 Newtonsoft.Json，底层 HttpContent.ReadAsAsync<T>不明白如何反序列化 IChild 类型的对象，后者是一个接口(interface)。如何向 Newtonsoft.Json 指定如何将 IChild 反序列化为具体类型？

Answer 1

您可以使用自定义 Converter告诉 JSON.NET 如何反序列化该接口(interface)的类型。下面的代码显示了一个示例。

public class StackOverflow_12197892
{
    public class Data
    {
        public IEnumerable<IChild> Children { get; set; }

        public override string ToString()
        {
            return string.Format("Data{{Children=[{0}]}}",
                string.Join(", ", Children.Select(c => string.Format("{0}/{1}", c.Name, c.IsFemale ? "girl" : "boy"))));
        }
    }
    public interface IChild
    {
        string Name { get; }
        bool IsFemale { get; }
    }
    public class Son : IChild
    {
        public Son(string name)
        {
            this.Name = name;
        }

        public string Name { get; private set; }
        public bool IsFemale { get { return false; } }
    }
    public class Daughter : IChild
    {
        public Daughter(string name)
        {
            this.Name = name;
        }

        public string Name { get; private set; }
        public bool IsFemale { get { return true; } }
    }
    class ChildConverter : Newtonsoft.Json.JsonConverter
    {
        public override bool CanConvert(Type objectType)
        {
            return typeof(IChild).IsAssignableFrom(objectType);
        }

        public override object ReadJson(Newtonsoft.Json.JsonReader reader, Type objectType, object existingValue, Newtonsoft.Json.JsonSerializer serializer)
        {
            JObject obj = serializer.Deserialize<JToken>(reader) as JObject;
            if (obj != null)
            {
                bool isFemale = obj["isFemale"].ToObject<bool>();
                string name = obj["name"].ToObject<string>();
                if (isFemale)
                {
                    return new Daughter(name);
                }
                else
                {
                    return new Son(name);
                }
            }
            else
            {
                return null;
            }
        }

        public override void WriteJson(Newtonsoft.Json.JsonWriter writer, object value, Newtonsoft.Json.JsonSerializer serializer)
        {
            throw new NotImplementedException();
        }
    }
    public static void Test()
    {
        Newtonsoft.Json.JsonSerializer serializer = new Newtonsoft.Json.JsonSerializer();
        serializer.Converters.Add(new ChildConverter());
        string json = "{'Children':[{'name':'John',isFemale:false},{'name':'Mary',isFemale:true}]}".Replace('\'', '\"');
        var obj = serializer.Deserialize(new StringReader(json), typeof(Data));
        Console.WriteLine(obj);
    }
}