httpcontext_example.cs

public class ContextAccessor : IContextAccessor
{
  public IDictionary<string, string> QueryString
  {
    // assume .AsDictionary() is an extension method that takes the QueryString struct and converts it to a Dictionary
    get { return HttpContext.Current.Request.QueryString.AsDictionary(); }
  }
}

public interface IContextAccessor
{
  IDictionary<string, string> QueryString { get; }
}

[ApiController]
[Route("api/test")
public class TestController : ControllerBase
{
  private readonly IContextAccessor _contextAccessor { get; set; }
  
  public TestController(IContextAccessor contextAccessor)
  {
    _contextAccessor = contextAccessor;
  }
  
  public IActionResult Get()
  {
    return Ok(_contextAccessor.QueryString["name"]);
  }
}