I have a class which has a many to many relationship with student. Please bare in mind this is a xarmain forms application talking to the client using NewtownSoft

public class Booking
{
    public int Id { get; set; }
    public int? DayOfWeek { get; set; }
    public DateTime? BookingDate { get; set; }
    public bool? IsAbsent { get; set; }
    public DateTime? Time { get; set; }
    public bool? HasCheckedIn { get; set; }
    public ICollection<Student> Students { get; set; }
    public bool? IsDeleted { get; set; }
    public bool? IsActive { get; set; }
    public string? CreatedBy { get; set; }
    public string? LastModifiedBy { get; set; }
    public DateTime? LastUpdatedDate { get; set; }
    public DateTime? CreatedDate { get; set; }
}

Student Class

public class Student
{
    public int Id { get; set; }
    public int? Type { get; set; }
    public string? FirstName { get; set; }
    public string? Surname { get; set; }
    public DateTime? DOB { get; set; }
    public decimal? Weight { get; set; }
    public decimal? Height { get; set; }
    public int? Gender { get; set; }
    public string? Photo { get; set; }
    public int? Age { get; set; }
    public ICollection<Booking> Bookings { get; set; }
    public bool? IsDeleted { get; set; }
    public ICollection<Notes>? Notes { get; set; }
    public decimal? TB { get; set; }
    public decimal? OP { get; set; }
    public decimal? PU { get; set; }
    public decimal? PB { get; set; }
    public decimal? BP { get; set; }
    public bool? IsActive { get; set; }
    public string? CreatedBy { get; set; }
    public string? LastModifiedBy { get; set; }
    public DateTime? LastUpdatedDate { get; set; }
    public DateTime? CreatedDate { get; set; }

}

I am adding that student to my api in the following way from the button click event.

private async void btnBookStudent_Clicked(object sender, EventArgs e)
{

 //if we want the booking to include our student we must add it to our colleciton.
 
    var test = Helpers.Dates.GetDateZeroTime(selectedBookingDate.Date).Add(timePicker.Time);
    var student = await api.GetStudentById(StudentId);
            

    var newBooking = new Booking
    {
            IsAbsent = false,
            IsActive = true,
            IsDeleted = false,
            Time = Helpers.Dates.
   GetDateZeroTime(selectedBookingDate.Date).  
   Add(timePicker.Time),
            DayOfWeek = DayNumber                 
                
    };
    newBooking.Students = new List<Student>();
    newBooking.Students.Add(student);
    await api.AddToBooking(newBooking);
    await DisplayAlert(Constants.AppName, "Booking Created For 
    Student", "OK");
 
}

However my client application is crashing out and not producing an error.

public async Task<HttpStatusCode> AddToBooking(Booking booking)
{
    HttpStatusCode statusCode = new HttpStatusCode();

    List<string> errors = new List<string>();
    var serializerSettings = new JsonSerializerSettings {
    ReferenceLoopHandling = 
    Newtonsoft.Json.ReferenceLoopHandling.Serialize};

   string json = 
   JsonConvert.SerializeObject(booking,Formatting.Indented, 
   serializerSettings);


    booking.CreatedBy = db.GetActiveUser();

    var httpContent = new StringContent(json, Encoding.UTF8,
    "application/json");
    //    AddAuthenicationHeader();
    // Do the actual request and await the response

    var httpResponse = await httpClient.PostAsync(Constants.BaseUrl   Constants.ApiSegmant   Constants.AddBooking, httpContent);
    statusCode = httpResponse.StatusCode;

    return statusCode;

   }

As said before in my previous post its not giving me an error my Xamarin forms c# android application its just crashing at the JsonConvert line.

I have seen some articles suggesting turning off reference loop handling works but it doesn't in my case as I need to add the student at time of the booking.

How do I get more details error information on what is happening I tried adding.

On my booking class but it doesn't even get fired?. A try catch doesn't catch it either.

[OnError]
internal void OnError(StreamingContext context, ErrorContext errorContext)
{
      var test = errorContext.Error;
}

I even tried [JsonIgnore] but i dont want that as I want the students to be with the bookings.

CodePudding user response：

There is a self-referencing loop, as both models reference each other and if Json.NET was to serialise the object, it'd be stuck between Booking and Student.

Try ignoring the bookings from being serialised in every student using [JsonIgnore].

public class Student
{
    public int Id { get; set; }
    public int? Type { get; set; }
    public string? FirstName { get; set; }
    public string? Surname { get; set; }
    public DateTime? DOB { get; set; }
    public decimal? Weight { get; set; }
    public decimal? Height { get; set; }
    public int? Gender { get; set; }
    public string? Photo { get; set; }
    public int? Age { get; set; }

    [JsonIgnore]
    public ICollection<Booking> Bookings { get; set; }
    
    public bool? IsDeleted { get; set; }
    public ICollection<Notes>? Notes { get; set; }
    public decimal? TB { get; set; }
    public decimal? OP { get; set; }
    public decimal? PU { get; set; }
    public decimal? PB { get; set; }
    public decimal? BP { get; set; }
    public bool? IsActive { get; set; }
    public string? CreatedBy { get; set; }
    public string? LastModifiedBy { get; set; }
    public DateTime? LastUpdatedDate { get; set; }
    public DateTime? CreatedDate { get; set; }

}