asp.net-mvc-4 – 用于继承类型的WebApi模型绑定

我正在寻找在WebApi中继承类型的模型绑定,而我真正想要做的是使用默认模型绑定来处理绑定(除了选择不能这样做的类型),但是我遗漏一些根本的东西

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,我会这样做：

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.

那么如何为WebApi版本做同样的呢？

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,我没有找到在实例化对象之后使用“标准”http绑定的好方法.我可以专门针对其他帖子中提到的JSON(Deserialising Json to derived types in Asp.Net Web API)或XML(Getting my Custom Model bound to my POST controller)进行处理,但在我看来,这是因为web api应该分离出来,而是 – 它只是不知道如何确定方式. (所有具体类型自然处理得很好.)

我是否忽略了一些明显的事情,我应该在实例化对象后引导BindModel调用？

解决方法

以下是我在我的类型中继承的一个示例,并且在某些设置(如使用KNownType属性装饰,Xml格式化程序的datacontractserializer需要)和TypeNameHandling设置之后,我们可以期待两个xml / json请求的一致行为.

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;
        }
    }
}