创建接受从参数类型（多态参数）派生的任何类型的参数的操作

Question

我想构建一个动态结构，供客户端在 Web 中询问服务器 API。我曾尝试使用以下代码来处理我的问题，但是，它不起作用。

How can I send a generic type like <travel> to service

How can I change server code (or all need to change client/server)?

PS:如果您看完我的问题，谢谢您的耐心等待。

客户代码

var serializer = new JavaScriptSerializer();    
var product = new travel() { travel_desc = "select * from travel" };    
var jsonText = serializer.Serialize(product);    
var client = new HttpClient();    
client.BaseAddress = new Uri("http://localhost:65370/");     
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));    
StringContent content = new StringContent(jsonText, Encoding.UTF8, "application/json");     

var z = client.PostAsync<travel>("api/bb", product, new JsonMediaTypeFormatter()).Result;

服务器代码，无效

public IHttpActionResult Post< T > (Object x) where T : new()    
{    
                ........................    
}

顺便说一句，没关系，但我不知道如何将发送到服务器

public IHttpActionResult Post(Object x)    
{    
                ........................    
}

错误信息
Client call server, server will be getting an error message " StatusCode: 404, ReasonPhrase: 'Not Found' "

 var z = client.PostAsync < travel > ("api/dd", product, new JsonMediaTypeFormatter()).Result; <--client

    public class ddController< T > : ApiController {public virtual void Post() {   ... }  } <---server    





  // sorry all , my English isn't very well , so I will try to use code to tell everyone how i want 
// in format situations,I will create 2 controller when I have 2 models(ex: users/product) , as following (client)
                var a = client.PostAsync("api/users", users, new JsonMediaTypeFormatter()).Result;
                var b = client.PostAsync("api/product", product, new JsonMediaTypeFormatter()).Result;

//and then when the users and product controllers was created the post code should be like as following (server)
                public IHttpActionResult Postusers(users travel) {}
                public IHttpActionResult Postproduct(product travel) {}

   //now i just want to create 1 controller for above  like as follwing 
                 var b = client.PostAsync<users/product>("api/all", product, new JsonMediaTypeFormatter()).Result;(client)

                 public IHttpActionResult Post<T>(Object ForAll) where T : new() {} (server)

Answer 1

JSON.NET，Web API JSON 序列化程序，能够在序列化对象时发送类型信息，并使用相同的信息对其进行反序列化。

它使用的技巧是包含一个 $type 属性作为 JSON 对象的第一个属性。

如果你想使用这个技术，你需要有一个基础class或者一个接口，例如ITravel，从它继承所有可能的classes，并且使用基础 class 或接口作为参数类型，像这样：

public interface ITravel
{
  public int TravelId { get; set; }
}

public class TravelTypeA : ITravel
{
  public int TravelId { get; set; }
  public string Destination { get; set; }
}

public class TravelTypeB : ITravel
{
  ...
}

[HttpPost]
public object PostMeATravel(ITravel travel)
{
    // check what type is travel with "is" or ".GetType()"
}

您还需要指示 JSON 在（反）序列化 ITravel 对象时包含类型信息。 (JSON TypeName Handling):

JsonSerializerSettings serializerSettings 
  = GlobalConfiguration.Configuration.Formatters
    .JsonFormatter.SerializerSettings;

serializerSettings.TypeNameHandling = TypeNameHandling.Auto;

然后你必须 post 一个带有 typeInformation 的 JSON，像这样：

{
  $type: 'SampleApp.TravelTypeA, SampleApp',
  TravelId: 22,
  Destination: 'La Almunia de Doña Godina'
}

当您这样做时，JSON.NET 将使用类型信息创建一个 TravelTypeA 对象，并将其作为参数传递给需要 ITravel 的操作。如果需要，您可以在操作中检查接收到的参数的类型，如下所示：if (travel.GetType().Name == "TravelTypeA") { ... }

查看此问答，了解有关如何执行此操作、其工作原理、此方法的优缺点以及替代方法的更多信息：Deserialising Json to derived types in Asp.Net Web API

注意：您可以使用优秀的 Postman 补充 Chrome 来测试 Web API 方法

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