How to use querystring within Blazor controller

I have the following code within my Blazor Server Project:

using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.Mvc;
using RouteAttribute = Microsoft.AspNetCore.Mvc.RouteAttribute;

namespace ProjectName.Controllers
{
    [Route("/getfile")]
    [ApiController]
    [Authorize]
    public class ReturnFileController : ControllerBase
    {

        [Parameter]
        [SupplyParameterFromQuery]
        public int? fileId { get; set; }

        [HttpGet()]
        public async Task<IActionResult> GetFile()
        {
            File file = GetFileAsync(fileId);
        }
    }
}

But the fileId is not filled when I go to .../getfile?fileId=12

How do I use a querystring within my controller?

>Solution :

I don’t typically try to bind action parameters directly to class members. Have you tried:

[HttpGet()]
public async Task<IActionResult> GetFile([FromQuery] int? fileId)
{
    if (fileId == null) { 
        //do something 
    }

    File file = GetFileAsync(fileId.Value);
}