Error: SyntaxError: Unexpected token

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 ------------ 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 ; });

Sachin Singh · Answer

The problem is you are not using return type in your method , use Task and everything will be ok. public async Task DeleteUserProfile() { string errorMessage = String.Empty ....... else { // The web api sent an error response. errorMessage = "Server error on deleting the user profile. Reason: " ; } } catch (Exception ex1) { } // Return a JSON object to show the error message. return Json(errorMessage, JsonRequestBehavior.AllowGet); } in ajax success if (!jQuery.isEmptyObject(data)) { do your stuff }

First Last · Answer

My code for resolving my issue (it no longer does a redirect and always sends back a JSON object): public async Task DeleteUserProfile() { string errorMessage = String.Empty; bool RedirectSwitch = false ; 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) { // Set the switch so that the AJAX call will go to the User controller. RedirectSwitch = true ; } else { // The web api sent an error response. errorMessage = "Server error on deleting the user profile. Reason: " + result.ReasonPhrase; } } } catch (Exception ex1) { Some code... } if (errorMessage != "" ) { // Set an error code which will initiate the AJAX function: 'error: function (error) {}'. Response.StatusCode = ( int )HttpStatusCode.InternalServerError; } // Creates JSON representation of anonymous data. // Return a JSON object. return Json( new { Redirect = RedirectSwitch, ErrorMessage = errorMessage }); } The Ajax: $.ajax({ type: 'POST' , url: '@Url.Action("DeleteUserProfile", "UserProfile")' , dataType: "json" , success: function (result) { if (result.Redirect) { // A successful delete - so go to the User controller. To the index action which returns the Views\User\User.cshtml. window.location.href = "/User/Index/" ; } }, error: function (error) { // Set the error message from the key/value pair set in the controller: ErrorMessage = errorMessage. $( "#jsonErrorMessage" ).text(error.responseJSON.ErrorMessage); // Show it. $( "#jsonErrorMessage" ).css( "display" , "block" ); } });

First Last · Answer

Sachin...sorry, I mistakenly left out the Task . It was there all along.

Kiran Mohanty · Answer

In success method, you can write it as if (jsondata) { // your logic when it has error } else { //logic when no error }

Error: SyntaxError: Unexpected token < in JSON