[c#] return error message with actionResult

MVC App, client makes request to server, error happens, want to send the msg back to the client. Tried HttpStatusCodeResult but just returns a 404 with no message, I need the details of the error sent back to the client.

public ActionResult GetPLUAndDeptInfo(string authCode)
{
    try
    {
        //code everything works fine
    }
    catch (Exception ex)
    {
         Console.WriteLine(ex.Message);
         return new HttpStatusCodeResult(404, "Error in cloud - GetPLUInfo" + ex.Message);
    }
}

Inside Controller Action you can access HttpContext.Response. There you can set the response status as in the following listing.

[HttpPost]
public ActionResult PostViaAjax()
{
    var body = Request.BinaryRead(Request.TotalBytes);

    var result = Content(JsonError(new Dictionary<string, string>()
    {
        {"err", "Some error!"}
    }), "application/json; charset=utf-8");
    HttpContext.Response.StatusCode = (int)HttpStatusCode.BadRequest;
    return result;
}

You need to return a view which has a friendly error message to the user

catch (Exception ex)
{
   // to do :log error
   return View("Error");
}

You should not be showing the internal details of your exception(like exception stacktrace etc) to the user. You should be logging the relevant information to your error log so that you can go through it and fix the issue.

If your request is an ajax request, You may return a JSON response with a proper status flag which client can evaluate and do further actions

[HttpPost]
public ActionResult Create(CustomerVM model)
{
  try
  {
   //save customer
    return Json(new { status="success",message="customer created"});
  }
  catch(Exception ex)
  {
    //to do: log error
   return Json(new { status="error",message="error creating customer"});
  }
} 

If you want to show the error in the form user submitted, You may use ModelState.AddModelError method along with the Html helper methods like Html.ValidationSummary etc to show the error to the user in the form he submitted.

IN your view insert

@Html.ValidationMessage("Error")

then in the controller after you use new in your model

var model = new yourmodel();
try{
[...]
}catch(Exception ex){
ModelState.AddModelError("Error", ex.Message);
return View(model);
}

One approach would be to just use the ModelState:

ModelState.AddModelError("", "Error in cloud - GetPLUInfo" + ex.Message);

and then on the view do something like this:

@Html.ValidationSummary()

where you want the errors to display. If there are no errors, it won't display, but if there are you'll get a section that lists all the errors.