Required query string parameter in ASP.NET Core

In ASP.NET Core 2.1 and above you can use top level parameters validation.
You can put attributes on parameters

    [HttpGet]
    public IActionResult GetDices([BindRequired, Range(1, 6)]int number)
    {
        if (!ModelState.IsValid)
        {
            return BadRequest("Invalid number");
        }

            return Ok(_diceRepo.GetDices(number));
    }

More about this
https://programmingcsharp.com/asp-net-parameter-validation/#Top-level_node_validation