将具有基类型的列表序列化为派生类型 json

Question

我有一个Web API控制器操作，它有一个类型为CommandMessage的参数。该类型有一个包含基本类型的列表，即 CommandBase。我的问题是我不能使它们成为派生类型，在这个例子中是MyCommand。

我正在使用Web API contrib项目中的JsonNetFormatter。它使用 Json.Net 作为序列化程序。

Web API 控制器：

public class CommandController : ApiController
{
    public HttpResponseMessage Post(CommandMessage command)
    {
        //command.Commands[0].GetType().Name is always "CommandBase" instead of "MyCommand"
        var message = new HttpResponseMessage(HttpStatusCode.OK)
                          {
                              Content = new StringContent(string.Format("Type of command 1 is '{0}'", command.Commands[0].GetType().FullName))
                          };
        return message;
    }
}

这是我的要求：

private void When()
    {
        using (client)
        {
            command = new MyCommand
                          {
                              CommandId = Guid.NewGuid(),
                              Id = Guid.NewGuid(),
                              Name = "Martin"
                          };
            var message = new CommandMessage(Guid.NewGuid(),new List<CommandBase> {command});
            var requestMessage = GetHttpRequestMessage(message);
            var task = client.PostAsync("http://localhost.:16218/api/command", requestMessage.Content);
            task.Wait();
            responseMessage = task.Result;
        }
    }
private static HttpRequestMessage GetHttpRequestMessage<T>(T data)
    {
        var mediaType = new MediaTypeHeaderValue("application/json");
        var jsonFormatter = new JsonNetFormatter(DefaultJsonSettings.Settings());
        var requestMessage = new HttpRequestMessage<T>(data, mediaType, new[] {jsonFormatter});
        return requestMessage;
    }

作为 JSON：

{
  "$type": "PostToBaseClassList.Models.CommandMessage, PostToBaseClassList",
  "Commands": [
    {
      "$type": "PostToBaseClassList.Models.MyCommand, PostToBaseClassList",
      "Id": "45923a41-0c15-46e3-907d-64dd06840539",
      "Name": "Martin"
    }
  ],
  "MessageId": "c873970a-8621-4223-806e-b809039438ab"
}

来自 API 控制器操作的返回消息为：

命令 1 的类型是"PostToBaseClassList.Models.CommandBase"

命令类：

 [DataContract]
[XmlRoot]
public class MyCommand : CommandBase
{
    private readonly string name;
    public MyCommand()
    {
    }
    public MyCommand(Guid id, string name)
    {
        this.name = name;
        Id = id;
    }
    [DataMember(Order = 1)]
    [XmlElement]
    public Guid Id { get; set; }
    [DataMember(Order = 2)]
    [XmlElement]
    public string Name { get; set; }
}
 [DataContract]
[KnownType("GetKnownTypes")]
public class CommandBase
{
    public Guid CommandId { get; set; }
    public static Type[] GetKnownTypes()
    {
        var query =
            from type in typeof (CommandBase).Assembly.GetTypes()
            where typeof (CommandBase).IsAssignableFrom(type)
            select type;
        var types = query.ToArray();
        return types;
    }
}
[DataContract]
[Serializable]
[XmlRoot]
public class CommandMessage
{
    public CommandMessage()
    {
    }
    public CommandMessage(Guid messageId, IEnumerable<CommandBase> commands)
    {
        MessageId = messageId;
        Commands = new List<CommandBase>(commands);
    }
    [DataMember]
    [XmlElement]
    public List<CommandBase> Commands { get; set; }
    [DataMember]
    [XmlElement]
    public Guid MessageId { get; set; }
}

Json.Net 设置：

//DefaultJsonSettings.Settings()
var settings = new JsonSerializerSettings
                           {
                               NullValueHandling = NullValueHandling.Ignore,
                               TypeNameHandling = TypeNameHandling.Objects,
                               Converters = new List<JsonConverter>
                                                {
                                                    new IsoDateTimeConverter
                                                        ()
                                                }
                           };
private static void RegisterFormatters(HttpConfiguration config)
    {
        var jsonNetFormatter = new JsonNetFormatter(DefaultJsonSettings.Settings());
        config.Formatters.Insert(0, jsonNetFormatter);
    }

有什么想法吗？

Answer 1

Json.NET 不

尊重KnownTypes属性，您必须提供自己的转换器。

此问题提供了几种不同的解决方案：使用 Json.NET 转换器反序列化属性

Answer 2

在我将这一行添加到 RegisterFormatters（） 后它起作用了

config.Formatters.Remove(config.Formatters.JsonFormatter);

这还不够

config.Formatters.Insert(0, jsonNetFormatter);

完整版

private void RegisterFormatters()
{
    config.Formatters.Remove(config.Formatters.JsonFormatter);
    var jsonNetFormatter = new JsonNetFormatter(DefaultJsonSettings.Settings());
    config.Formatters.Insert(0, jsonNetFormatter);
}