ASP.NET Web API failed to serialize the response content

Question

I'm making a UWP application, using Entity Framework, with WebApi about Students and Courses. I have amany-to-many relationship between my Students and Courses. I tried to route an action that combines students and their courses from the database tables. I want to GET the information about the Students and just the name of the Course they're enrolled in.

Here is my error message:

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

Here is my custom route in my custom controller file.

StudentsCoursesController

public class StudentsCoursesController : ApiController
{
    private DataContext db = new DataContext();

    //GET: api/Students/Courses
    [HttpGet]
    [Route("api/Students/Courses")]
    [ResponseType(typeof(Students[]))]
    public IHttpActionResult GetstudentsCourse()
    {
        var Student = from st in db.Students.Include("Courses")
                      select new { st.Id, st.FirstName, st.LastName, st.Courses };

        return Ok(Student);
    }
}

This is the DataContext constructor:

DataContext:

public DataContext() : base("Database")
    {
        Configuration.ProxyCreationEnabled = false;
        Configuration.LazyLoadingEnabled = false;
        Database.SetInitializer(new LibraryDBInitializer());
    }

Here is the error message I get in my Web Api:

I'm not getting any errors in my code, but I'm not getting any results either. Any ideas what could be wrong? I have a feeling the error is in my API code (the controller).

Thanks

If a student has many courses and a course has many students the serializer is probably getting into an infinite loop. Have a look at https://stackoverflow.com/questions/12641386/failed-to-serialize-the-response-in-web-api. — user1378730, Nov 06 '17 at 23:38
Method's response type expects an array of students so returning an IQueryable could be the problem, adding toArray at the end might do it. — etuncoz, Nov 07 '17 at 01:35
https://stackoverflow.com/questions/12641386/failed-to-serialize-the-response-in-web-api — Akash KC, Nov 07 '17 at 02:18

score 0 · Answer 1 · answered Nov 07 '17 at 02:08

0

You should cast your LINQ query to array -

Student[]

answered Nov 07 '17 at 02:08

Nick Reshetinsky

447
2
13

score 0 · Answer 2 · answered Nov 07 '17 at 03:10

I want to GET the information about the Students and just the name of the Course they're enrolled in.

If you want just the names of the courses then select only the names of the courses

var Students = db.Students.Include("Courses").Select(st =>
                  new { 
                      Id = st.Id, 
                      FirstName = st.FirstName, 
                      LastName = st.LastName, 
                      Courses = st.Courses.Select(course => course.Name).ToArray() 
                  }).ToArray();

Pedro Drewanz · Answer 3 · 2017-11-08T22:21:47.940

0

It is a Serialization problem.

As it is said in this answer you cannot serialize, by default, anonymous types to xml.

In your cliente, change the contente type to "application/json"

edited Nov 08 '17 at 22:21

answered Nov 08 '17 at 22:03

Pedro Drewanz

1,242
13
14

ASP.NET Web API failed to serialize the response content

3 Answers3