title: ASP.NET - API 400 error on GET request
body: <p>I have this Controller:</p>
  
  <pre><code>namespace Cantrel.Application.CantrelSearchApi.Controllers
  {
      [Route("api/[controller]")]
      [Authorize]
      public class MonitorsController : Controller
      {
          private readonly IMonitoringApiService monitoringService;
          private readonly IClientsApiService clientsService;
          private readonly ILogger&lt;MonitorsController&gt; logger;
  
          public MonitorsController(IMonitoringApiService monitoringService,
              IClientsApiService clientsService,
              ILogger&lt;MonitorsController&gt; logger)
          {
              this.monitoringService = monitoringService;
              this.clientsService = clientsService;
              this.logger = logger;
          }
  
    [HttpGet("{id}")]
      public async Task&lt;IActionResult&gt; Get(string id)
      {
          if (string.IsNullOrEmpty(null))
          {
              return BadRequest("No id was provided. Please provide a valid monitor id or subject id.");
          }
  
          try
          {
              MonitorDto monitor;
  
              if (Guid.TryParse(id, out Guid monitorId))
              {
                  monitor = await GetByMonitorId(monitorId);
              }
              else
              {
                  monitor = await GetBySubjectId(id);
              }
  
              if (monitor == null)
              {
                  return NotFound();
              }
  
              return Json(monitor);
          }
          catch (Exception ex)
          {
              logger.LogError($"[{Request.Path.Value}]: {ex.ToString()}");
              return new StatusCodeResult(500);
          }
      }
  </code></pre>
  
  <p>I make the following call in Postman:</p>
  
  <pre><code>GET: {{api}}/Monitors/ABCDEFGH-1234-4567-8901-ABCDEFGHIJKL
  </code></pre>
  
  <p>Instead of the expected return of information on that monitor I receive a <code>400 Bad Request</code> error with the message <code>No id was provided. Please provide a valid monitor id or subject id</code>.</p>
  
  <p>I'm not sure I understand how this is happening.  The string is clearly neither NULL or empty.</p>
  
  <p>Please let me know if there is any other classes' code I should provide to assist in diagnosis.</p>