Error: SyntaxError: Unexpected token < in JSON

Question

I know why I am getting this message as the AJAX is completing and expects JSON coming back.

 

However, I coded the controller action method such that if all is good, redirects to another view. If there is an error is found, return JSON - an error message.

 

From the AJAX perspective as I am learning, it will expect JSON back regardless of a good (the redirect) or error situation (I return JSON).

 

So how do I code that up in the AJAX to recognize that no JSON was returned when it is a good situation as I do the redirect and do not programmatically return anything?

 

------------

 

The action method executes successfully in the sense that it does the delete, executes the redirect but gets caught on the return and I get the message:

 

    Error: SyntaxError: Unexpected token < in JSON 

 

------------

 

My actions method is:

 

I have

    Task

If I try

    Task

I get an error on the redirect statement. 

public async Task DeleteUserProfile()
        {
            string errorMessage = String.Empty;

            try
            {
                Some code to call the web api...

                using (var client = new HttpClient())
                {
                    Some code...

                    // Call the web api - HTTP POST.
                    HttpResponseMessage result = await client.PostAsync(restOfUrl, argsData);

                    if (result.IsSuccessStatusCode)
                    {
                        return RedirectToAction("Index", "User");
                    }
                    else
                    {
                        // The web api sent an error response.
                        errorMessage = "Server error on deleting the user profile. Reason: " + result.ReasonPhrase;
                    }
                }
            }
            catch (Exception ex1)
            {
               Some code...
            }

            // Return a JSON object to show the error message.
            return Json(errorMessage, JsonRequestBehavior.AllowGet);
        }

My view that has the AJAX that calls the method: 

<input class="btn btn-danger deleteButton" value="Delete Your Profile">

There is a Modal window and on a Yes, executes the AJAX. And I was thinking it would only come back if I pushed the JSON with the error message. 

$('.btn-yes11').click(function() {
                $('#myModal11').modal('hide');

                $.ajax({
                    type: 'POST',
                    url: '@Url.Action("DeleteUserProfile", "UserProfile")',
                    dataType: "json",
                    success: function(jsondata) {
                        if (jsondata.length > 0)
                        {
                            // Set the error message.
                            $("#jsonErrorMessage").text(jsondata);
                            // Show.
                            $("#jsonErrorMessage").css("display", "block");
                        }
                        else
                        {
                            // Hide.
                            $("#jsonErrorMessage").css("display", "none");
                        }
                     },
                    error: function(xhr, ajaxOptions, thrownError) {
                        alert('Critical Error: something is wrong in the call to DeleteUserProfile for delete! Status: ' + xhr.status + '. Error: ' + thrownError.toString() + '. Response Text: ' + xhr.responseText);
                    }
                });

                return true;
            });