asp.net core api - how to distinguish between `api/cars` and `api/cars?color=red` calls with [FromQuery] object

Question

I am using [FromQuery] atribute in controller's Get method:

//CarsController, etc..
[HttpGet]
public async Task<ActionResult<IEnumerable<CarsDto>>> Get([FromQuery] CarsParameter? carsParam = null)
{
    //param is always not null here
}

Inside the method I need to distinguish between api/cars and api/cars?color=red calls. Problem is, that carsParam object is never null, so I cannot say if the Color="" (defailt value) is intended to be empty string or it's because of the call was api/cars

CarsParameter is a simple class:

public class CarsParameter
{
  public string Color {get; set;} = "";
  //more params here
}

Yes, I can use different path, like api/cars/withParams?color=red, but i am looking for more subtle solution.

Answer 1

I need to distinguish between api/cars and api/cars?color=red calls. Problem is, that carsParam object is never null

Please note that default model binding starts by looking through the sources for the key carsParam.Color. If that isn't found, it looks for Color without a prefix, which cause the issue.

To achieve your requirement, you can try to specify prefix explicitly, like below.

public async Task<ActionResult<IEnumerable<CarsDto>>> Get([FromQuery][Bind(Prefix = "carsParam")] CarsParameter? carsParam = null)
{

Request to api/cars?color=red&carsParam.color=yellow&carsParam.brand=test and following is test result