我正在寻找在WebApi中处理继承类型的模型绑定，我真正想做的是使用默认模型绑定来处理绑定（除了选择它无法执行此操作的类型） ，但我遗漏了一些基本的东西。
所以说我有类型：
public abstract class ModuleVM
{
public abstract ModuleType ModuleType { get; }
}
public class ConcreteVM : ModuleVM
{
}
使用MVC控制器，我会做这样的事情：
public class ModuleMvcBinder : DefaultModelBinder
{
protected override object CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType)
{
if (modelType == typeof(ModuleVM))
{
// Just hardcoding the type for simplicity
Type instantiationType = typeof(ConcreteVM);
var obj = Activator.CreateInstance(instantiationType);
bindingContext.ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(null, instantiationType);
bindingContext.ModelMetadata.Model = obj;
return obj;
}
return base.CreateModel(controllerContext, bindingContext, modelType);
}
}
[AttributeUsage( AttributeTargets.Class | AttributeTargets.Enum | AttributeTargets.Interface | AttributeTargets.Parameter | AttributeTargets.Struct | AttributeTargets.Property, AllowMultiple = false, Inherited = false)]
public class ModuleMvcBinderAttribute : CustomModelBinderAttribute
{
public override IModelBinder GetBinder()
{
return new ModuleMvcBinder();
}
}
然后使用控制器上的属性，一切都很好，我正在利用DefaultModelBinder进行实际工作，我基本上只是提供正确的对象实例化。
那么我如何为WebApi版本做同样的事情呢？
如果我使用自定义模型绑定器（例如Error implementing a Custom Model Binder in Asp.Net Web API），我的问题是（我相信）在BindModel方法中，我没有找到一个好的方法来使用“标准”http绑定一旦我实例化物体。我可以像其他帖子中所建议的那样专门为JSON（Deserialising Json to derived types in Asp.Net Web API）或XML（Getting my Custom Model bound to my POST controller）做这件事，但在我看来，由于web api应该将其分离，并且它是 - 它只是不知道如何确定类型。 （所有具体类型自然都处理得很好。）
我是否忽略了一些明显的事情，我应该在实例化对象后指导BindModel调用？
答案 0 :(得分：3)
以下是我在我的类型中继承的示例，在一些设置之后（如使用KnownType属性进行装饰，Xml formatter的datacontractserializer需要）和Json格式化程序上的TypeNameHandling设置，我们可以预期两个xml / json请求之间的行为是一致的。
using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Net;
using System.Net.Http;
using System.Net.Http.Formatting;
using System.Net.Http.Headers;
using System.Runtime.Serialization;
using System.Web.Http;
using System.Web.Http.SelfHost;
namespace Service
{
class Service
{
private static HttpSelfHostServer server = null;
private static string baseAddress = string.Format("http://{0}:9095/", Environment.MachineName);
static void Main(string[] args)
{
HttpSelfHostConfiguration config = new HttpSelfHostConfiguration(baseAddress);
config.Routes.MapHttpRoute("Default", "api/{controller}/{id}", new { id = RouteParameter.Optional });
config.IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.Always;
config.Formatters.JsonFormatter.SerializerSettings.TypeNameHandling = TypeNameHandling.Objects;
try
{
server = new HttpSelfHostServer(config);
server.OpenAsync().Wait();
Console.WriteLine("Service listenting at: {0} ...", baseAddress);
TestWithHttpClient("application/xml");
TestWithHttpClient("application/json");
Console.ReadLine();
}
catch (Exception ex)
{
Console.WriteLine("Exception Details:\n{0}", ex.ToString());
}
finally
{
if (server != null)
{
server.CloseAsync().Wait();
}
}
}
private static void TestWithHttpClient(string mediaType)
{
HttpClient client = new HttpClient();
MediaTypeFormatter formatter = null;
// NOTE: following any settings on the following formatters should match
// to the settings that the service's formatters have.
if (mediaType == "application/xml")
{
formatter = new XmlMediaTypeFormatter();
}
else if (mediaType == "application/json")
{
JsonMediaTypeFormatter jsonFormatter = new JsonMediaTypeFormatter();
jsonFormatter.SerializerSettings.TypeNameHandling = TypeNameHandling.Objects;
formatter = jsonFormatter;
}
HttpRequestMessage request = new HttpRequestMessage();
request.RequestUri = new Uri(baseAddress + "api/students");
request.Method = HttpMethod.Get;
request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(mediaType));
HttpResponseMessage response = client.SendAsync(request).Result;
Student std = response.Content.ReadAsAsync<Student>().Result;
Console.WriteLine("GET data in '{0}' format", mediaType);
if (StudentsController.CONSTANT_STUDENT.Equals(std))
{
Console.WriteLine("both are equal");
}
client = new HttpClient();
request = new HttpRequestMessage();
request.RequestUri = new Uri(baseAddress + "api/students");
request.Method = HttpMethod.Post;
request.Content = new ObjectContent<Person>(StudentsController.CONSTANT_STUDENT, formatter);
request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue(mediaType));
Student std1 = client.SendAsync(request).Result.Content.ReadAsAsync<Student>().Result;
Console.WriteLine("POST and receive data in '{0}' format", mediaType);
if (StudentsController.CONSTANT_STUDENT.Equals(std1))
{
Console.WriteLine("both are equal");
}
}
}
public class StudentsController : ApiController
{
public static readonly Student CONSTANT_STUDENT = new Student() { Id = 1, Name = "John", EnrolledCourses = new List<string>() { "maths", "physics" } };
public Person Get()
{
return CONSTANT_STUDENT;
}
// NOTE: specifying FromBody here is not required. By default complextypes are bound
// by formatters which read the body
public Person Post([FromBody] Person person)
{
if (!ModelState.IsValid)
{
throw new HttpResponseException(Request.CreateErrorResponse(HttpStatusCode.BadRequest, this.ModelState));
}
return person;
}
}
[DataContract]
[KnownType(typeof(Student))]
public abstract class Person : IEquatable<Person>
{
[DataMember]
public int Id { get; set; }
[DataMember]
public string Name { get; set; }
public bool Equals(Person other)
{
if (other == null)
return false;
if (ReferenceEquals(this, other))
return true;
if (this.Id != other.Id)
return false;
if (this.Name != other.Name)
return false;
return true;
}
}
[DataContract]
public class Student : Person, IEquatable<Student>
{
[DataMember]
public List<string> EnrolledCourses { get; set; }
public bool Equals(Student other)
{
if (!base.Equals(other))
{
return false;
}
if (this.EnrolledCourses == null && other.EnrolledCourses == null)
{
return true;
}
if ((this.EnrolledCourses == null && other.EnrolledCourses != null) ||
(this.EnrolledCourses != null && other.EnrolledCourses == null))
return false;
if (this.EnrolledCourses.Count != other.EnrolledCourses.Count)
return false;
for (int i = 0; i < this.EnrolledCourses.Count; i++)
{
if (this.EnrolledCourses[i] != other.EnrolledCourses[i])
return false;
}
return true;
}
}
}