[c#] Failed to serialize the response in Web API with Json

I am working with ASP.NET MVC 5 Web Api. I want consult all my users.

I wrote api/users and I receive this:

"The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; charset=utf-8'"

In WebApiConfig, already I added these lines:

HttpConfiguration config = new HttpConfiguration();
config.Formatters.XmlFormatter.SupportedMediaTypes.Remove(appXmlType);
config.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore; 

But it still doesn't work.

My function for return data is this:

public IEnumerable<User> GetAll()
{
    using (Database db = new Database())
    {
        return db.Users.ToList();
    }
}

I resolved it using this code to WebApiConfig.cs file

var json = config.Formatters.JsonFormatter;
json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects; 
config.Formatters.Remove(config.Formatters.XmlFormatter);

Just put following lines in global.asax:

GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;  
GlobalConfiguration.Configuration.Formatters.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);

Import

using System.Data.Entity;

While all these answers above are correct, one may want to check the InnerException > ExceptionMessage.

If it says something like this "The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.". This could be an issue because of default behavior of the EF.

By assigning LazyLoadingEnabled = false in your DbContext constructor will do the trick.

public class MyDbContext : DbContext
{
  public MyDbContext()
  {
    this.Configuration.LazyLoadingEnabled = false;
  }
}

For more detailed reading about EagerLoading and LazyLoading behavior of EF refer this MSDN Article.

Add the below line

this.Configuration.ProxyCreationEnabled = false;

Two way to use ProxyCreationEnabled as false.

1. Add it inside of DBContext Constructor

   public ProductEntities() : base("name=ProductEntities")
   {
       this.Configuration.ProxyCreationEnabled = false;
   }
   

OR

2. Add the line inside of Get method

   public IEnumerable<Brand_Details> Get()
   {
       using (ProductEntities obj = new ProductEntities())
       {
           this.Configuration.ProxyCreationEnabled = false;
           return obj.Brand_Details.ToList();
       }
   }
   

I basically add one line which they are

• entities.Configuration.ProxyCreationEnabled = false;

to UsersController.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using UserDataAccess;

namespace SBPMS.Controllers
{
    public class UsersController : ApiController
    {


        public IEnumerable<User> Get() {
            using (SBPMSystemEntities entities = new SBPMSystemEntities()) {
                entities.Configuration.ProxyCreationEnabled = false;
                return entities.Users.ToList();
            }
        }
        public User Get(int id) {
            using (SBPMSystemEntities entities = new SBPMSystemEntities()) {
                entities.Configuration.ProxyCreationEnabled = false;
                return entities.Users.FirstOrDefault(e => e.user_ID == id);
            }
        }
    }
}

Use AutoMapper...

public IEnumerable<User> GetAll()
    {
        using (Database db = new Database())
        {
            var users = AutoMapper.Mapper.DynamicMap<List<User>>(db.Users);
            return users;
        }
    }

Use the following namespace:

using System.Web.OData;

Instead of :

using System.Web.Http.OData;

It worked for me

public class UserController : ApiController
{

   Database db = new Database();

   // construction
   public UserController()
   {
      // Add the following code
      // problem will be solved
      db.Configuration.ProxyCreationEnabled = false;
   }

   public IEnumerable<User> GetAll()
    {
            return db.Users.ToList();
    }
}

You will have to define Serializer Formatter within WebApiConfig.cs available in App_Start Folder like

Adding config.Formatters.Remove(config.Formatters.XmlFormatter); // which will provide you data in JSON Format

Adding config.Formatters.Remove(config.Formatters.JsonFormatter); // which will provide you data in XML Format

There's also this scenario that generate same error:

In case of the return being a List<dynamic> to web api method

Example:

public HttpResponseMessage Get()
{
    var item = new List<dynamic> { new TestClass { Name = "Ale", Age = 30 } };

    return Request.CreateResponse(HttpStatusCode.OK, item);
}

public class TestClass
{
    public string Name { get; set; }
    public int Age { get; set; }
}

So, for this scenario use the [KnownTypeAttribute] in the return class (all of them) like this:

[KnownTypeAttribute(typeof(TestClass))]
public class TestClass
{
    public string Name { get; set; }
    public int Age { get; set; }
}

This works for me!

In case: If adding code to WebApiConfig.cs or Global.asax.cs doesn't work for you:

.ToList();

Add .ToList() function.

I tried out every solution but following worked for me:

var allShops = context.shops.Where(s => s.city_id == id)**.ToList()**;
return allShops;

I hope, it helps.

In my case I solved recreating the database. I made some changes in a model and launching Update-Database in Package Manager Console I got the following Error:

"The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_dbo.Activities_dbo.Projects_ProjectId". The conflict occurred in database "TrackEmAllContext-20190530144302", table "dbo.Projects", column 'Id'."

My personal favorite: Just add the code below to App_Start/WebApiConfig.cs. This will return json instead of XML by default and also prevent the error you had. No need to edit Global.asax to remove XmlFormatter etc.

The 'ObjectContent`1' type failed to serialize the response body for content type 'application/xml; charset=utf-8

config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html"));

Given right answer is one way to go, however it is an overkill when you can fix it by one config settings.

Better to use it in the dbcontext constructor

public DbContext() // dbcontext constructor
            : base("name=ConnectionStringNameFromWebConfig")
{
     this.Configuration.LazyLoadingEnabled = false;
     this.Configuration.ProxyCreationEnabled = false;
}

Asp.Net Web API Error: The 'ObjectContent`1' type failed to serialize the response body for content type 'application/xml; charset=utf-8'

To add to jensendp's answer:

I would pass the entity to a user created model and use the values from that entity to set the values in your newly created model. For example:

public class UserInformation {
   public string Name { get; set; }
   public int Age { get; set; }

   public UserInformation(UserEntity user) {
      this.Name = user.name;
      this.Age = user.age;
   }
}

Then change your return type to: IEnumerable<UserInformation>

in my case, it was fixed when I removed the virtual keyword before my navigation properties, I mean the reference tables. so I changed

public virtual MembershipType MembershipType { get; set; }

to:

public MembershipType MembershipType { get; set; }

Adding this in your Application_Start() method of Global.asax file should solve the problem

protected void Application_Start()
{
    GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings
        .ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
    GlobalConfiguration.Configuration.Formatters
        .Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter); 
// ...
}

METHOD 2: [Not recommended]
If you are working with EntityFramework, you can disable proxy in your DbContext class constructor. NOTE: this code wll be removed if you update the model

public class MyDbContext : DbContext
{
  public MyDbContext()
  {
    this.Configuration.ProxyCreationEnabled = false;
  }
}

If you are working with EF, besides adding the code below on Global.asax

GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings
    .ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
GlobalConfiguration.Configuration.Formatters
    .Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);          

Dont`t forget to import

using System.Data.Entity;

Then you can return your own EF Models

Simple as that!

Another case where I received this error was when my database query returned a null value but my user/view model type was set as non-nullable. For example, changing my UserModel field from int to int? resolved.

I don't like this code:

foreach(var user in db.Users)

As an alternative, one might do something like this, which worked for me:

var listOfUsers = db.Users.Select(r => new UserModel
                         {
                             userModel.FirstName = r.FirstName;
                             userModel.LastName = r.LastName;

                         });

return listOfUsers.ToList();

However, I ended up using Lucas Roselli's solution.

Update: Simplified by returning an anonymous object:

var listOfUsers = db.Users.Select(r => new 
                         {
                             FirstName = r.FirstName;
                             LastName = r.LastName;
                         });

return listOfUsers.ToList();

Visual Studio 2017 or 2019 is totally unthoughtful on this, because Visual Studio itself requires the output to be in json format, while Visual Studio's default format is "XmlFormat" (config.Formatters.XmlFormatter).

Visual Studio should do this automatically instead of giving developers so much trouble.

To correct this problem, go to the WebApiConfig.cs file, and add

var json = config.Formatters.JsonFormatter; json.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.Objects; config.Formatters.Remove(config.Formatters.XmlFormatter);

after "config.MapHttpAttributeRoutes();" in the Register(HttpConfiguration config) method. This would allow your project to produce json output.

Use [Serializable] for class:

Example:

[Serializable]
public class UserModel {
    public string Name {get;set;}
    public string Age {get;set;}
}

It worked for me!

Solution that worked for me:

1. Use [DataContract] for class and [DataMember] attributes for each property to serialize. This is enough to get Json result (for ex. from fiddler).

2. To get xml serialization write in Global.asax this code:

   var xml = GlobalConfiguration.Configuration.Formatters.XmlFormatter; xml.UseXmlSerializer = true;

3. Read this article, it helped me to understand serialization: https://www.asp.net/web-api/overview/formats-and-model-binding/json-and-xml-serialization

In my case I have had similar error message:

The 'ObjectContent`1' type failed to serialize the response body for content type 'application/xml; charset=utf-8'.

But when I dig deeper in it, the issue was:

Type 'name.SomeSubRootType' with data contract name 'SomeSubRootType://schemas.datacontract.org/2004/07/WhatEverService' is not expected. Consider using a DataContractResolver if you are using DataContractSerializer or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to the serializer.

The way I solved by adding KnownType.

[KnownType(typeof(SomeSubRootType))]
public partial class SomeRootStructureType

This was solved inspired from this answer.

Reference: https://msdn.microsoft.com/en-us/library/ms730167(v=vs.100).aspx

Add this code to global.asax below on Application_Start:

Update from .Ignore to .Serialize . It must work.

GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Serialize;
            GlobalConfiguration.Configuration.Formatters.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);

This also happens when the Response-Type is not public! I returned an internal class as I used Visual Studio to generate me the type.

internal class --> public class