Properties are missing while serializing to json, but its visible in Quick View in Debug mode

Question

The response of Web Api is missing few fields, however, the fields are visible in Debug mode. Do I need to decorate the model with anything specific?

Model:

    public class SampleModel
    {
        public string? SampleModelString { get; set; }
        public SampleModel1? SampleModel1Object { get; set; }
    }
    public class SampleModel1 : List<SampleModel2>
    {
        public SampleModel3? SampleModel3Object { get; set; }
        public string? SampleModel1String { get; set; }
    }
    public class SampleModel2
    {
        public string? SampleModel2String { get; set; }
    }
    public class SampleModel3 : List<SampleModel4>
    {        
    }
    public class SampleModel4
    {
        public string? SampleModel4String { get; set; }
    }

Api Code:

        [HttpGet]
        public IActionResult Get()
        {
            SampleModel sampleModel = new SampleModel();

            sampleModel.SampleModelString = "SampleModel.String";
            sampleModel.SampleModel1Object = new SampleModel1();
            sampleModel.SampleModel1Object.Add(new SampleModel2 { SampleModel2String = "SampleModel2.String1" });
            sampleModel.SampleModel1Object.Add(new SampleModel2 { SampleModel2String = "SampleModel2.String2" });

            sampleModel.SampleModel1Object.SampleModel1String = "SampleModel1.String";
            sampleModel.SampleModel1Object.SampleModel3Object = new SampleModel3();
            sampleModel.SampleModel1Object.SampleModel3Object.Add(new SampleModel4 { SampleModel4String = "SampleModel4.String1" });
            sampleModel.SampleModel1Object.SampleModel3Object.Add(new SampleModel4 { SampleModel4String = "SampleModel4.String2" });            

            return Ok(sampleModel);
        }

Debug mode:

Output:

Answer 1

Your SampleModel1 is a List with extra properties. This can't be reflected to json as is. You can refactor your code to contain List<SampleModel2> instead of inheriting from it.

 public class SampleModel1
    {
        public List<SampleModel2> SampleModel2ListObject {get; set;}
        public SampleModel3? SampleModel3Object { get; set; }
        public string? SampleModel1String { get; set; }
    }

---

Update Based on your comment: You can wrap it into another class and re-assign properties. You may need to refactor it to make it safe/read-only.

public class SampleModel1Wrapper
{
    private SampleModel1 _base;

    public List<SampleModel2> SampleModel2ListObject
    {
        get
        {
            return (List<SampleModel2>)_base;
        }
        set
        {
            _base = value;
        }
    }

    public SampleModel3? SampleModel3Object 
    {
        get
        {
            return _base.SampleModel3Object;
        }
        set
        {
            _base.SampleModel3Object = value;
        }
    }
    public string? SampleModel1String
    {
        get
        {
            return _base.SampleModel1String;
        }
        set
        {
            _base.SampleModel1String = value;
        }
    }