Не могу сериализовать объект Controller Web API

public class IDKEY
    {
        [Key]
        public int id { get; set; }
        //[Required]
...
 
        //
        [ForeignKey("virtual_ApplicationUser")]
        public string id_virtual_ApplicationUser { get; set; }
        public virtual ApplicationUser virtual_ApplicationUser { get; set; }
        //
 
    }
}

[Route("api/APIConnect/{id_client:int}")]
 
        public IDKEY GetIDKEY(int id_client)
        {
            ApplicationContext context = new ApplicationContext();
            var i = context.DbSet_IDKEY.Find(id_client);
            return i;
        }

//public string GetIDKEY(int id_client)
        //{
        //  ApplicationContext context = new ApplicationContext();
        //  var i = context.DbSet_IDKEY.Find(id_client);
        //  //IDKEY book = db.Books.Find(id);
        //  return i.id_name;
        //}

{
  "Message": "An error has occurred.",
  "ExceptionMessage": "The 'ObjectContent`1' type failed to serialize the response body for content type 'application/json; charset=utf-8'.",
  "ExceptionType": "System.InvalidOperationException",
  "StackTrace": null,
  "InnerException": {
    "Message": "An error has occurred.",
    "ExceptionMessage": "Self referencing loop detected for property 'virtual_IDKEY' with type 'System.Data.Entity.DynamicProxies.IDKEY_E752B34CE7C5F3956767518F4FFE204E3F36D05F09E32E760256031C3F9B532A'. Path 'virtual_Client'.",
    "ExceptionType": "Newtonsoft.Json.JsonSerializationException",
    "StackTrace": "   в Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.CheckForCircularReference(JsonWriter writer, Object value, JsonProperty property, JsonContract contract, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n   в Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.CalculatePropertyValues(JsonWriter writer, Object value, JsonContainerContract contract, JsonProperty member, JsonProperty property, JsonContract& memberContract, Object& memberValue)\r\n   в Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject(JsonWriter writer, Object value, JsonObjectContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n   в Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n   в Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeObject(JsonWriter writer, Object value, JsonObjectContract contract, JsonProperty member, JsonContainerContract collectionContract, JsonProperty containerProperty)\r\n   в Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.SerializeValue(JsonWriter writer, Object value, JsonContract valueContract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerProperty)\r\n   в Newtonsoft.Json.Serialization.JsonSerializerInternalWriter.Serialize(JsonWriter jsonWriter, Object value, Type objectType)\r\n   в Newtonsoft.Json.JsonSerializer.SerializeInternal(JsonWriter jsonWriter, Object value, Type objectType)\r\n   в System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n   в System.Net.Http.Formatting.JsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, Encoding effectiveEncoding)\r\n   в System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStream(Type type, Object value, Stream writeStream, HttpContent content)\r\n   в System.Net.Http.Formatting.BaseJsonMediaTypeFormatter.WriteToStreamAsync(Type type, Object value, Stream writeStream, HttpContent content, TransportContext transportContext, CancellationToken cancellationToken)\r\n--- Конец трассировка стека из предыдущего расположения, где возникло исключение ---\r\n   в System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   в System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   в System.Web.Http.WebHost.HttpControllerHandler.<WriteBufferedResponseContentAsync>d__1b.MoveNext()"
  }
}

public class ApplicationContext: IdentityDbContext<ApplicationUser>
    {
        public ApplicationContext() { 
            Configuration.ProxyCreationEnabled = false; 
        }
        
        public ApplicationContext(string conectionString) : base(conectionString) {     }