Custom model binder with inheritance using Web API and RavenDB - asp.net-mvc-4

Question

I'm developing a simple web app where I need to bind all types implementing and interface of a specific type. My interface has one single property like this
public interface IContent {
string Id { get;set; }
}
a common class using this interface would look like this
public class Article : IContent {
public string Id { get;set; }
public string Heading { get;set; }
}
to be clean here the article class is just one of many different classes implementing IContent so therefor I need a generic way of storing and updating these types.
So in my controller I have the put method like this
public void Put(string id, [System.Web.Http.ModelBinding.ModelBinder(typeof(ContentModelBinder))] IContent value)
{
// Store the updated object in ravendb
}
and the ContentBinder
public class ContentModelBinder : System.Web.Http.ModelBinding.IModelBinder {
public bool BindModel(HttpActionContext actionContext, ModelBindingContext bindingContext) {
actionContext.ControllerContext.Request.Content.ReadAsAsync<Article>().ContinueWith(task =>
{
Article model = task.Result;
bindingContext.Model = model;
});
return true;
}
}
The code above does not work because it does not seem to get hold of the Heading property even though if I use the default model binder it binds the Heading correctly.
So, in the BindModel method I guess I need to load the correct object from ravendb based on the Id and then update the complex object using some kind of default model binder or so? This is where I need some help.

Answer 1

Marcus, following is an example which would work fine for both Json and Xml formatter.
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; }
// this is ignored
public DateTime DateOfBirth { 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;
}
}
}

Answer 2

I used #kiran-challa solution and added TypeNameHandling on Json media type formatter's SerializerSettings.