Ошибка сериализации json - Не ошибается лишь тот, кто ничего не делает!

I have the following exception generated inconsistently but frequently:

System.Exception: Serialization error - One or more errors occurred., Unexpected character encountered while parsing value: <. Path '', line 0, position 0., System.AggregateException: One or more errors occurred. ---> Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: <. Path '', line 0, position 0.
   at Newtonsoft.Json.JsonTextReader.ParseValue()
   at Newtonsoft.Json.JsonTextReader.Read()
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.ReadForType(JsonReader reader, JsonContract contract, Boolean hasConverter)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
   at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
   at Microsoft.AspNet.SignalR.Client.Transports.TransportHelper.b__1(String raw)
   at Microsoft.AspNet.SignalR.TaskAsyncHelper.<>c__DisplayClass19`2.b__17(Task`1 t)
   at Microsoft.AspNet.SignalR.TaskAsyncHelper.TaskRunners`2.<>c__DisplayClass42.b__41(Task`1 t)
   --- End of inner exception stack trace ---
   at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions)
   at System.Threading.Tasks.Task.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
   **at Project.Services.NotificationService.SignalObjectToUser(Object data, String username, Boolean isTypingNotification)
---> (Inner Exception #0) Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: <. Path '', line 0, position 0.**
   at Newtonsoft.Json.JsonTextReader.ParseValue()
   at Newtonsoft.Json.JsonTextReader.Read()
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.ReadForType(JsonReader reader, JsonContract contract, Boolean hasConverter)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
   at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
   at Microsoft.AspNet.SignalR.Client.Transports.TransportHelper.b__1(String raw)
   at Microsoft.AspNet.SignalR.TaskAsyncHelper.<>c__DisplayClass19`2.b__17(Task`1 t)

The important bit:

**at Project.Services.NotificationService.SignalObjectToUser(Object data, String username, Boolean isTypingNotification)
---> (Inner Exception #0) Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: <. Path '', line 0, position 0.**

My code there:

private void SignalObjectToUser(object data, string username, bool isTypingNotification = false) {
        try {
            _hubConnection = new HubConnection(_baseUrl);
            _hubConnection.CookieContainer = new CookieContainer();
            _hubConnection.CookieContainer.Add(_cookie);
            _hubProxy = _hubConnection.CreateHubProxy("appHub");
            _hubConnection.Start().Wait();
            string serialized = null;
            try {
                List<string> errors = new List<string>();
                serialized = JsonConvert.SerializeObject(data, new JsonSerializerSettings() {
                    Error = delegate(object sender, ErrorEventArgs args) {
                        errors.Add(args.ErrorContext.Error.Message);
                        args.ErrorContext.Handled = true;
                        Elmah.ErrorSignal.FromCurrentContext().Raise(new Exception("Delegated serialization error - " + args.ErrorContext.Error.Message));
                    }
                });
                _hubProxy.Invoke((isTypingNotification ? "SendTypingNotification" : "SendClientNotification"), serialized, username).Wait();
            }
            catch (Exception exception) {
                Elmah.ErrorSignal.FromCurrentContext().Raise(new Exception("Serialization error - " + exception.Message + ", " + exception.InnerException.Message + ", " + exception.ToString()));
                throw new Exception("Messaging Error");
            }
        }
        catch (Exception e) {
            Elmah.ErrorSignal.FromCurrentContext().Raise(new Exception("Serialization error - " + e.Message + ", " + e.InnerException.Message + ", " + e.ToString()));
            throw new Exception("Messaging Error");
        }
    }

I’m trying to figure out what exactly is causing this issue though. I don’t know what key/value pair is generating the exception. How can I gather more instructive details here?

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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();
    }
}

chakeda

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asked Apr 16, 2014 at 2:56

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!

Markus

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answered Mar 1, 2015 at 1:08

Lucas RoselliLucas Roselli

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When it comes to returning data back to the consumer from Web Api (or any other web service for that matter), I highly recommend not passing back entities that come from a database. It is much more reliable and maintainable to use Models in which you have control of what the data looks like and not the database. That way you don’t have to mess around with the formatters so much in the WebApiConfig. You can just create a UserModel that has child Models as properties and get rid of the reference loops in the return objects. That makes the serializer much happier.

Also, it isn’t necessary to remove formatters or supported media types typically if you are just specifying the «Accepts» header in the request. Playing around with that stuff can sometimes make things more confusing.

Example:

public class UserModel {
    public string Name {get;set;}
    public string Age {get;set;}
    // Other properties here that do not reference another UserModel class.
}

answered Apr 16, 2014 at 3:12

jensendpjensendp

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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);

answered Jan 14, 2016 at 18:48

Bimal DasBimal Das

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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();
    }
}

answered Sep 16, 2016 at 14:21

AykutAykut

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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);

answered Mar 23, 2018 at 13:28

aemreaemre

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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();

Donut

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answered Apr 9, 2015 at 13:40

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;
  }
}

answered Jan 12, 2018 at 4:31

Er Suman GEr Suman G

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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!

answered Oct 24, 2014 at 17:20

AlexAlex

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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"));

answered Aug 12, 2016 at 11:24

OgglasOgglas

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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;

סטנלי גרונן

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answered Jun 13, 2020 at 6:30

Use AutoMapper…

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

answered Sep 4, 2015 at 4:30

ProximoProximo

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Use the following namespace:

using System.Web.OData;

Instead of :

using System.Web.Http.OData;

It worked for me

Mayuso

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answered Nov 3, 2016 at 10:40

Add the below line

this.Configuration.ProxyCreationEnabled = false;

Two way to use ProxyCreationEnabled as false.

Add it inside of DBContext Constructor

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

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();
    }
}

barbsan

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answered Jun 13, 2019 at 5:55

MR.SMR.S

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Use [Serializable] for class:

Example:

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

It worked for me!

answered Jul 22, 2019 at 16:48

MsxmaniaMsxmania

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Solution that worked for me:

Use [DataContract] for class and [DataMember] attributes for each property to serialize. This is enough to get Json result (for ex. from fiddler).
To get xml serialization write in Global.asax this code:

var xml = GlobalConfiguration.Configuration.Formatters.XmlFormatter; xml.UseXmlSerializer = true;
Read this article, it helped me to understand serialization:
https://www.asp.net/web-api/overview/formats-and-model-binding/json-and-xml-serialization

answered Nov 16, 2016 at 7:07

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>

answered May 5, 2015 at 13:27

Greg AGreg A

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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.

answered Dec 29, 2017 at 12:39

B BhatnagarB Bhatnagar

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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

answered Feb 19, 2018 at 12:21

Maytham FahmiMaytham Fahmi

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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);
            }
        }
    }
}

answered Apr 24, 2019 at 9:36

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

answered Jul 28, 2019 at 11:47

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.

answered Oct 14, 2015 at 14:49

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

answered Nov 15, 2017 at 15:52

VaniceVanice

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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.

answered Apr 30, 2019 at 20:27

William HouWilliam Hou

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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’.»

answered May 30, 2019 at 14:46

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.

answered Jun 5, 2019 at 10:24

CatalystCatalyst

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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; }

answered Apr 3, 2020 at 18:21

Hadi R.Hadi R.

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