Cannot get a response from a Web API call - asp.net-mvc

Question

I have the following in the TreeController controller in a small web API:
[HttpGet("GetDirectories")]
public IActionResult GetDirectories()
{
var baseDir = _config["QuickShare:BaseDir"];
if (string.IsNullOrWhiteSpace(baseDir))
{
throw new InvalidOperationException("'QuickShare:BaseDir' is not configured");
}
var ret = GetDirectories(baseDir); ;
return Json(ret);
}
private List<DirectoryInfo> GetDirectories(string parentDir)
{
var dirInfo = new DirectoryInfo(parentDir);
return dirInfo.GetDirectories("*", SearchOption.TopDirectoryOnly).ToList();
}
When I try and call this action from Postman, I get told
Could not get any response There was an error connecting to
http://localhost:59243/api/Tree/GetDirectories.
Now the default, test, controller that comes with the project template is unchanged:
[Route("api/[controller]")]
public class ValuesController : Controller
{
// GET api/values
[HttpGet]
public IEnumerable<string> Get()
{
return new string[] {"value1", "value2"};
}
...
}
And when I have the API running in Visual Studio, I can get a proper response from the Values controller, but not from the TreeController, yet they are almost exactly the same. And, when I call the Tree/GetDirectories` action, a breakpoint in that action method is hit, and I can single step through the very few lines that my method has, and they all execute fine.
The problem only becomes apparent when that last line of the action executes:
return Json(ret);
Then I get shown that Postman Could not get any response despite no exception being raised; while debugging the code, it looks like everything should work fine, and the requests to the Values controller work fine.

Answer 1

Your action method should return either the specific result type (JsonResult when you return Json ) or IActionResult.
Example:
[HttpGet("GetDirectories")]
public JsonResult GetDirectories()
{
var baseDir = _config["QuickShare:BaseDir"];
if (string.IsNullOrWhiteSpace(baseDir))
{
throw new InvalidOperationException("'QuickShare:BaseDir' is not configured");
}
var ret = GetDirectories(baseDir);
return Json(ret);
}
OR
[HttpGet("GetDirectories")]
public IActionResult GetDirectories()
{
var baseDir = _config["QuickShare:BaseDir"];
if (string.IsNullOrWhiteSpace(baseDir))
{
throw new InvalidOperationException("'QuickShare:BaseDir' is not configured");
}
var ret = GetDirectories(baseDir) ;
return Ok(ret);
}
You can get more help from Microsoft Documentation: Formatting Response Data