.Net Core 3.0 possible object cycle was detected which is not supported

Question

I have 2 entities that are related as one to many

public class Restaurant {
   public int RestaurantId {get;set;}
   public string Name {get;set;}
   public          


        

Answer 1

I came across this issue and I was confused because I have another application running the same code, only difference was I wanted to use await this time, and in the last application I used ConfigureAwait(false).GetAwaiter().GetResult();

So by removing await and adding ConfigureAwait(false).GetAwaiter().GetResult() at the end of the Async method I was able to resolve this.

Answer 2

.NET Core 3.1 Install the package Microsoft.AspNetCore.Mvc.NewtonsoftJson

Startup.cs Add service

services.AddControllers().AddNewtonsoftJson(options =>
    options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
);

Answer 3

This happens because of the 2 way relationship between your data model when it comes to be JSON serialized.

You should not return your data model diectly. Map it to a new response model then return it.

Answer 4

public class Reservation{ 
public int ReservationId {get;set;} 
public int RestaurantId {get;set;} 
[JsonIgnore]
public Restaurant Restaurant {get;set;} 

Above worked also. But I prefer the following

services.AddControllers().AddNewtonsoftJson(options =>
    options.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore
);

Because first we need to add the attribute to all the models we may have the cyclic reference.

Answer 5

Getting the setting JSON serialisation options on startup to work is probably a preferred way as you will likely have similar cases in the future. In the meantime however you could try add data attributes to your model so it's not serialised: https://www.newtonsoft.com/json/help/html/PropertyJsonIgnore.htm

public class Reservation{ 
    public int ReservationId {get;set;} 
    public int RestaurantId {get;set;} 
    [JsonIgnore]
    public Restaurant Restaurant {get;set;} 
}

Answer 6

This worked using System.Text.Json

var options = new JsonSerializerOptions()
        {
            MaxDepth = 0,
            IgnoreNullValues = true,
            IgnoreReadOnlyProperties = true
        };

Using options to serialize

objstr = JsonSerializer.Serialize(obj,options);