Here is the model class

 public class SingleOrder
 {
     [JsonProperty("order")]
     public OneOrder? OneOrder { get; set; }
 }
 public class OneOrder
 {
     [JsonProperty("id")]
     public double? Id { get; set; }
     public string? email { get; set; }
     public string? tags { get; set; }
     public List<OneLineItem>? line_items { get; set; }

 }

Here in controller I am trying to initialize it and use it:

 public IActionResult Cancel(double? id)
 {
     id = 5768551825658;
     SingleOrder EmptyObject = new SingleOrder();
     EmptyObject.OneOrder.Id = id;      //Neither initializing with constructor not this way
 }