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Why asp.net core sending empty object as response?

When I debug the code in VS, the cities list, which I am returning have 3 objects in it along with the properties. When I call this endpoint I am receiving a response of 3 list items of empty objects.
How to resolve this issue?
Model Class:
public class City
{
public string CityName;
public string AssociatedCities;
public string Province;
public int Status;
public City(string cityName, string associatedCities, string province, int status)
{
this.CityName = cityName;
this.AssociatedCities = associatedCities;
this.Province = province;
this.Status = status;
}
}
Endpoint:
[HttpGet]
[Route("cities")]
public ActionResult<IEnumerable<City>> GetCities()
{
return Ok(Cities);
}
This is how I am calling the endpoint
getCities() {
this.http.get<City[]>('/api/wizard/cities')
.subscribe(result => {
console.log(result);
this.cities = result;
}, error => console.error('Something went wrong : ' + error));
}
The response I get:
The response that is needed:
[
{
"SearchCity": "Toronto",
"AssociatedCities": "Ajax, Whitby, Toronto, Mississauga, Brampton",
"Province": "ON",
"Status": 1
},
{
"SearchCity": "Vancouver",
"AssociatedCities": "Vancouver, Vancouver City",
"Province": "BC",
"Status": 1
}
]
I have tried this already: Fresh ASP.NET Core API returns empty JSON objects

System.Text.Json currently does not support serialization/deserialization of fields and non-parameter-less, non-default constructors.
Your example model uses both fields and a non-default constructor. If you need to use a custom constructor for some reason, you would need to implement your own JsonConverter<T> to support that. This doc might be helpful for that:
https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json-migrate-from-newtonsoft-how-to#deserialize-to-immutable-classes-and-structs
Only public properties with public getters/setters are supported along with the default, parameter-less constructor (what is referred to as Plain_old_CLR_object (POCO)). Note: If you are only serializing (i.e. writing), the setters generally don't have to be public.
Properties are different from fields (and contain getters/setters).
Here is the fix:
public class City
{
public string CityName { get; set; }
public string AssociatedCities { get; set; }
public string Province { get; set; }
public int Status { get; set; }
}

In my case, I just added this in my ConfigureServices method in Startup.cs (I am using Dot Net 5.0)
services.AddControllers().AddNewtonsoftJson();

Based on the fact that all your action does is return Cities, which presumably is a property or field defined on your controller, I'm going to take a shot in the dark and assume that you're setting that in another request and expecting it to still be there in this request. That's not how it works. The controller is instantiated and disposed with each request, so anything set to it during the lifetime of a request will not survive. As a result, Cities has nothing in this request, so you get an empty response.
If you need a list of cities in the action, then you should query those in that action. Also, for what it's worth, System.Text.Json does not currently support serializing fields, as others have mentioned in the comments, but you may still use JSON.NET instead, which does. See: https://learn.microsoft.com/en-us/aspnet/core/migration/22-to-30?view=aspnetcore-3.1&tabs=visual-studio#jsonnet-support

Can C# Web API Deserialize Object in URI that Contains a Dictionary

I am attempting to pass a complex object in a GET request. The C# model object looks like this:
public class GetRequest
{
public string ID { get; set; }
public List<string> RequestedFields { get; set; }
public Dictionary<string, List<string>> RequestedGrids { get; set; }
}
Looking at the request in Chrome I see the following under "Query String Parameters":
ID: 1
RequestedFields[]: someTxtField
RequestedFields[]: someOtherField
RequestedGrids[someGrid][]: keyColumn
RequestedGrids[someGrid][]: someDataColumn
I would expect such a request to be deserialized correctly as the parameter in the following action:
[HttpGet]
[ActionName("get")]
public Dictionary<string,object> GetStuff([FromUri] GetRequest get_req)
However, whenever a request enters this action, the RequestedGrids property of the parameter always has a count of 0, while the other properties are populated fine. Is there a way to make this work?
Addition
The object going into the JQuery $.get call looks like this:
{ ID: p_key, RequestedFields: p_page.dataIds, RequestedGrids: p_page.grids }
Where RequestedFields is a plain array of strings and RequestedGrids is a plain object where each object property value is an array of strings.

When you are needing to send this much data, especially complex data, it is best to send the data as part of the body of a POST request. This way, you can make sure that the structure matches completely and can easily convert to/from JSON format.

What does the input look like on the GET? Dictionary types are sort of painful to deserialize in general - see Deserialize JSON string to Dictionary<string,object> for details...

The easiest method to accomplish this seems to be to just pass a JSON query string instead of using the auto-binding. So the action looks like this:
[HttpGet]
[ActionName("get")]
public Dictionary<string, object> GetStuff(string get_str)
{
var get_req = JsonConvert.DeserializeObject<GetRequest>(get_str);
//Do ur stuff
}
And JS looks like this:
$.get('<action path>', { get_str: JSON.stringify(get_obj) }, ...

JSON Serialization of URI Type in WebAPI 2 ODATA 3 C# Project

I'm seeing C# URI types serialized to JSON in an ODATA 3 controller in my WebAPI 2 project as an array of segments that does not include the domain. I've tried everything I can think of to change this (including fiddling with the serialization settings and even trying out the contract serializer instead of JSON.Net). Nothing seems to change the behavior. Note, I am not using .Net Core. Here is a code sample, condensed into a single snippet.
namespace WebApplication1.Controllers
{
public class MyObject
{
public Uri Url { get; set; }
public string Name { get; set; }
public string ID { get; set; }
}
public class MyObjectsController : ODataController
{
private static ODataValidationSettings _validationSettings = new ODataValidationSettings();
public IHttpActionResult GetMyObjects(ODataQueryOptions<MyObject> queryOptions)
{
try
{
queryOptions.Validate(_validationSettings);
return Ok<IEnumerable<MyObject>>(new List<MyObject>() { new MyObject() { ID="asdf", Name="123rwe", Url = new Uri("http://www.webapp.com/sites/page.html") } });
}
catch (ODataException ex)
{
return BadRequest(ex.Message);
}
}
}
}
This generates the following JSON in the browser:
{
"odata.metadata":"http://localhost:51607/odata/$metadata#MyObjects","value":[
{
"Url":{
"Segments":[
"/","sites/","page.html"
]
},"Name":"123rwe","ID":"asdf"
}
]
}
This is what I'd like (without changing the Url property to a string):
{
"odata.metadata":"http://localhost:51607/odata/$metadata#MyObjects","value":[
{
"Url":"http://www.webapp.com/sites/page.html","Name":"123rwe","ID":"asdf"
}
]
}
Any thoughts?
UPDATE:
Further research is suggesting that serialization behavior for URI types in WebAPI ODATA is controlled by the odataentityreferencelink and odataentityreferencelinkserializer classes. Specifically, URI type appear to be converted to odataentityreferencelink types which are then serialized in the manner I posted above (as an array of segments not including the root domain). I still need to know how to change this behavior, however the documentation for these two classes is not proving helpful. Last, I've confirmed this problem is not specific to the JSON output format. The serialization behavior for both XML/Atom and JSON are identical: URIs are broken down into an array of segments.

MS Premier support provided a final answer to this which I'll share below.
There is no option to directly JSON serialize an URI type, normally it would be broken into array of segments as you are observing in your code
The domain name will be eliminated as a normal scenario
The option you can go for is to create a custom URI Converter deriving from JSONConverter which is a part of Newtonsoft.Json namespace

How to post a dynamic JSON property to a C# ASP.Net Core Web API using MongoDB?

How to post a dynamic JSON property to a C# ASP.Net Core Web API using MongoDB?
It seems like one of the advantages of MongoDB is being able to store anything you need to in an Object type property but it doesn't seem clear how you can get the dynamic property info from the client ajax post through a C# Web API to MongoDB.
We want to allow an administrator to create an Event with Title and Start Date/Time but we also want to allow the user to add custom form fields using Reactive Forms for whatever they want such as t-shirt size or meal preference... Whatever the user may come up with in the future. Then when someone registers for the event, they post EventID and the custom fields to the Web API.
We can have an Event MongoDB collection with _id, event_id, reg_time, and form_fields where form_fields is an Object type where the dynamic data is stored.
So we want to POST variations of this JSON with custom FormsFields:
Variation 1:
{
"EventId": "595106234fccfc5fc88c40c2",
"RegTime":"2017-07-21T22:00:00Z",
"FormFields": {
"FirstName": "John",
"LastName": "Public",
"TShirtSize": "XL"
}
}
Variation 2:
{
"EventId": "d34f46234fccfc5fc88c40c2",
"RegTime":"2017-07-21T22:00:00Z",
"FormFields": {
"Email": "John.Public#email.com",
"MealPref": "Vegan"
}
}
I would like to have an EventController with Post action that takes a custom C# EventReg object that maps to the JSON above.
EventController:
[HttpPost]
public void Post([FromBody]EventReg value)
{
eventService.AddEventRegistration(value);
}
EventReg Class:
public class EventReg
{
public EventReg()
{
FormFields = new BsonDocument();
}
[BsonId]
[BsonRepresentation(BsonType.ObjectId)]
public string EventRegId { get; set; }
[BsonElement("EventId")]
[BsonRepresentation(BsonType.ObjectId)]
public string EventId { get; set; }
[BsonElement("reg_time")]
public DateTime RegTime
{
set; get;
}
[BsonElement("form_fields")]
public MongoDB.Bson.BsonDocument FormFields { get; set; }
}
EventService
public string AddEventRegistration(EventReg eventReg)
{
this.database.GetCollection<EventReg>("event_regs").InsertOne(eventReg);
return eventReg.EventRegId;
}
Right now, if I post to the controller, my EventReg is null because it must not know how to map my JSON FormFields properties to a BsonDocument.
What type can I use for FormFields?
Can I have the FormFields property be a BsonDocument and is there an easy way to map the Web API parameter to that?
Is there an example of how some custom serializer might work in this case?
We could maybe use a dynamic type and loop through the posted properties but that seems ugly. I have also seen the JToken solution from a post here but that looks ugly also.
If MongoDB is meant to be used dynamically like this, shouldn't there be a clean solution to pass dynamic data to MongoDB? Any ideas out there?

In ASP.NET Core 3.0+ Newtonsoft.Json is not the default JSON serializer anymore. Therefore I would use JsonElement:
[HttpPost("general")]
public IActionResult Post([FromBody] JsonElement elem)
{
var title = elem.GetProperty("title").GetString();
...

The JToken example works to get data in but upon retrieval it causes browsers and Postman to throw an error and show a warning indicating that content was read as a Document but it was in application/json format. I saw the FormFields property being returned as {{"TShirtSize":"XL"}} so maybe double braces was a problem during serialization.
I ended up using the .NET ExpandoObject in the System.Dynamic namespace. ExpandoObject is compatible with the MongoDB BsonDocument so the serialization is done automatically like you would expect. So no need for weird code to manually handle the properties like the JToken example in the question.
I still believe that a more strongly typed C# representation should be used if at all possible but if you must allow any JSON content to be sent to MongoDB through a Web API with a custom C# class as input, then the ExpandoObject should do the trick.
See how the FormFields property of EventReg class below is now ExpandoObject and there is no code to manually handle the property of the object being saved to MongoDB.
Here is the original problematic and overly complex JToken code to manually populate an object with standard type properties and a dynamic FormFields property:
[HttpPost]
public void Post([FromBody]JToken token)
{
if (token != null)
{
EventReg eventReg = new EventReg();
if (token.Type == Newtonsoft.Json.Linq.JTokenType.Object)
{
eventReg.RegTime = DateTime.Now;
foreach (var pair in token as Newtonsoft.Json.Linq.JObject)
{
if (pair.Key == "EventID")
{
eventReg.EventId = pair.Value.ToString();
}
else if (pair.Key == "UserEmail")
{
eventReg.UserEmail = pair.Value.ToString();
}
else
{
eventReg.FormFields.Add(new BsonElement(pair.Key.ToString(), pair.Value.ToString()));
}
}
}
//Add Registration:
eventService.AddEventRegistration(eventReg);
}
}
Using ExpandoObject removes the need for all of this code. See the final code below. The Web API controller is now 1 line instead of 30 lines of code. This code now can insert and return the JSON from the Question above without issue.
EventController:
[HttpPost]
public void Post([FromBody]EventReg value)
{
eventService.AddEventRegistration(value);
}
EventReg Class:
public class EventReg
{
public EventReg()
{
FormFields = new ExpandoObject();
}
[BsonId]
[BsonRepresentation(BsonType.ObjectId)]
public string EventRegId { get; set; }
[BsonElement("event_id")]
[BsonRepresentation(BsonType.ObjectId)]
public string EventId { get; set; }
[BsonElement("user_email")]
public string UserEmail { get; set; }
[BsonElement("reg_time")]
public DateTime RegTime{ get; set; }
[BsonElement("form_fields")]
public ExpandoObject FormFields { get; set; }
}
EventService:
public string AddEventRegistration(EventReg eventReg)
{
this.database.GetCollection<EventReg>("event_regs").InsertOne(eventReg);
return eventReg.EventRegId;
}

If you are not sure about the type of Json you are sending i.e. if you are dealing with dynamic json. then the below approach will work.
Api:
[HttpPost]
[Route("demoPath")]
public void DemoReportData([FromBody] JObject Jsondata)
Http client call from .net core app:
using (var httpClient = new HttpClient())
{
return await httpClient.PostAsJsonAsync(serviceUrl,
new demoClass()
{
id= "demoid",
name= "demo name",
place= "demo place"
};).ConfigureAwait(false);
}

You can define FormFields as a string and send data to the API in string format after converting JSON to string:
"{\"FirstName\":"John\",\"LastName\":\"Public\",\"TShirtSize\":\"XL\"}"
Then in your controller parse the string to BsonDocument
BsonDocument.Parse(FormFields);
I would use AutoMapper to automate the conversion between the dto and the document

Restsharp: Deserialize json object with less/more fields than some class

I'm using Restsharp to deserialize some webservice responses, however, the problem is that sometimes this webservices sends back a json response with a few more fields. I've manage to come around this so far by adding all possible field to my matching model, but this web service will keep adding/removing fields from its response.
Eg:
Json response that works:
{
"name": "Daniel",
"age": 25
}
Matching model:
public class Person
{
public string name { get; set; }
public int age { get; set; }
}
This works fine: Person person = deserializer.Deserialize<Person>(response);
Now suppose the json response was:
{
"name": "Daniel",
"age": 25,
"birthdate": "11/10/1988"
}
See the new field bithdate? Now everything goes wrong. Is there a way to tell to restsharp to ignore those fields that are not in the model?

If there's that much variation in the fields you're getting back, perhaps the best approach is to skip the static DTOs and deserialize to a dynamic. This gist provides an example of how to do this with RestSharp by creating a custom deserializer:
// ReSharper disable CheckNamespace
namespace RestSharp.Deserializers
// ReSharper restore CheckNamespace
{
public class DynamicJsonDeserializer : IDeserializer
{
public string RootElement { get; set; }
public string Namespace { get; set; }
public string DateFormat { get; set; }
public T Deserialize<T>(RestResponse response) where T : new()
{
return JsonConvert.DeserializeObject<dynamic>(response.Content);
}
}
}
Usage:
// Override default RestSharp JSON deserializer
client = new RestClient();
client.AddHandler("application/json", new DynamicJsonDeserializer());
var response = client.Execute<dynamic>(new RestRequest("http://dummy/users/42"));
// Data returned as dynamic object!
dynamic user = response.Data.User;
A simpler alternative is to use Flurl.Http (disclaimer: I'm the author), an HTTP client lib that deserializes to dynamic by default when generic arguments are not provided:
dynamic d = await "http://api.foo.com".GetJsonAsync();
In both cases, the actual deserialization is performed by Json.NET. With RestSharp you'll need to add the package to your project (though there's a good chance you have it already); Flurl.Http has a dependency on it.