How to hide a property in a C# class from appearing in the JSON response body of a method that returns IActionResult?

Question

I have defined a ProblemDetails class. I construct an object of this class and return from my Http triggered Azure function upon error.

I have defined a convenience property HasDetail to tell if the object has any detail meaning if the object is empty. However, i don't want this property to be included in the response body. I have applied the [JsonIgnore] attribute as well hoping it will not expose that particular property but i still see this property in the response body. How do i stop this?

Note: The code and the response are below I am using system.text.json

Class:

public class ProblemDetails
{
    public string Type { get; set; }
    public string Title { get; set; }
    public int? Status { get; set; }
    public string Detail { get; set; }
    public string Instance { get; set; }
    [JsonIgnore]
    public bool HasDetail { 
        get 
        {
            return !result;
        }  
    }
}

Response body as JSON:

{
    "type": "https://aaa/codes",
    "title": "Input Not Provided",
    "status": 400,
    "detail": "Please provide a group name or groupId.",
    "instance": "",
    "hasDetail": true
}

Azure Function declaration

[OpenApiResponseWithBody(statusCode: HttpStatusCode.OK,
    contentType: "application/json",
    bodyType: typeof(bool),
    Description = "The OK response.")]
[FunctionName(FunctionNames.SomeName)]
public async Task<IActionResult> SomeName(
    [HttpTrigger(AuthorizationLevel.Function, "get", Route = null)] HttpRequest req)
    {
        // do something
    }