Develop Reference

How to return the same status code from a second API call

I have an ASP.NET Core API calling a second API.
I throw an exception in my services layer, if there is an error from the second API:
var response = await httpClient.SendAsync(request); //call second API
if (!response.IsSuccessStatusCode)
{
//return HTTP response with StatusCode = X, if response.StatusCode == X
throw new HttpRequestException(await response.Content.ReadAsStringAsync());
//this always returns 400
}
How can I throw an exception that will return a response with the same status code from the second API call?
If I use HttpRequestException it will always return 400, even if the response object had StatusCode = 500.
EDIT:
The first API endpoint looks like this:
public async Task<ActionResult<HttpResponseMessage>> CreateTenancy([FromBody]TenancyRequest tenancy)
{
//Make some calls...
return Created(string.Empty, new { TenancyID = newTenancyExternalId });
}
The second API endpoint looks like this:
[HttpPost]
public IHttpActionResult CreateTenancy([FromBody]TenancyDTO tenancyDTO)
{
var tenancy = GetTenancy();
return Created(string.Empty, tenancy);
}
I've tried using throw new HttpResponseException(response); but this removes the descriptive Exception message, the payload ends up like this:
{
"Code": 500,
"CorrelationId": "2df08016-e5e3-434a-9136-6824495ed907",
"DateUtc": "2020-01-30T02:02:48.4428978Z",
"ErrorMessage": "Processing of the HTTP request resulted in an exception. Please see the HTTP response returned by the 'Response' property of this exception for details.",
"ErrorType": "InternalServerError"
}
I'd like to keep the ErrorMessage value in the original payload:
{
"Code": 400,
"CorrelationId": "ff9466b4-8c80-4dab-b5d7-9bba1355a567",
"DateUtc": "2020-01-30T03:05:13.2397543Z",
"ErrorMessage": "\"Specified cast is not valid.\"",
"ErrorType": "BadRequest"
}
The end goal is to have this returned:
{
"Code": 500,
"CorrelationId": "ff9466b4-8c80-4dab-b5d7-9bba1355a567",
"DateUtc": "2020-01-30T03:05:13.2397543Z",
"ErrorMessage": "\"Specified cast is not valid.\"",
"ErrorType": "InternalServerError"
}

I tried something simple as changing the return type of the API endpoint and returning the object as it when there is an error. Otherwise, build your own HttpResponseMessage and return that. This snippet below uses text but you can use a serializer to serialize other content if you have.
public async Task<HttpResponseMessage> Test(string str)
{
var httpClient = new HttpClient();
var request = new HttpRequestMessage(HttpMethod.Get, $"myAPI that returns different errors 400, 404, 500 etc based on str");
var response = await httpClient.SendAsync(request);
if (!response.IsSuccessStatusCode)
return response;
// do something else
return new HttpResponseMessage(System.Net.HttpStatusCode.OK) { Content = new StringContent("Your Text here") };
}
Other approach of using Filters
The other approach of using IHttpActionResult as your return type, you can use Filters to conform all your HttpResponseMessages to IHttpActionResult.
Filter: Create a separate cs file and use this filter definition.
public class CustomObjectResponse : IHttpActionResult
{
private readonly object _obj;
public CustomObjectResponse(object obj)
{
_obj = obj;
}
public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
HttpResponseMessage response = _obj as HttpResponseMessage;
return Task.FromResult(response);
}
}
and in your API, you would use your filter like so,
public async Task<IHttpActionResult> Test(string str)
{
var httpClient = new HttpClient();
var request = new HttpRequestMessage(HttpMethod.Get, $"http://localhost:4500/api/capacity/update-mnemonics/?mnemonic_to_update={str}");
var response = await httpClient.SendAsync(request);
if (!response.IsSuccessStatusCode)
return new CustomObjectResponse(response);
// Other Code here
// Return Other objects
KeyValuePair<string, string> testClass = new KeyValuePair<string, string>("Sheldon", "Cooper" );
return new OkWithObjectResult(testClass);
// Or Return Standard HttpResponseMessage
return Ok();
}

You could simply make your API call and copy its response code into something compatible with IStatusCodeActionResult.
An alternative s to throw a custom exception. Create something like
public class ApiCallException : Exception
{
public APiCallException(int statusCode, ...)
{
ApiStatusCode = statusCode;
}
int ApiStatusCode { get; }
...
}
and copy over the status code from your API result, and then throw the exception.
var response = await httpClient.SendAsync(request); //call second API
if (!response.IsSuccessStatusCode)
{
var content = await response.Content.ReadAsStringAsync();
throw new ApiCallException(500, content);
}
You can then register an exception filter to deal with the result when calling AddMvc.
services.AddMvc(options => options.Filters.Add<ExceptionFilter>());
where ExceptionFilter could be something like
public class ExceptionFilter : IExceptionFilter
{
// ...
public void OnException(ExceptionContext context)
{
if (context.Exception is ApiCallException ace)
{
var returnObject = CreateReturnObjectSomehow();
context.Result = new ObjectResult(returnObject) { StatusCode = ace.StatusCode };
}
else
{
// do something else
}
}
}

Thanks Jawad and Kit for providing great answers which helped me work out the solution below:
Turns out there was some middleware handling the exception:
public async Task Invoke(HttpContext httpContext)
{
try
{
await _next(httpContext);
}
catch (Exception exception)
{
if (httpContext.Response.HasStarted) throw;
var statusCode = ConvertExceptionToHttpStatusCode(exception);
httpContext.Response.Clear();
httpContext.Response.StatusCode = (int)statusCode;
httpContext.Response.ContentType = "application/json";
if (statusCode != HttpStatusCode.BadRequest)
{
_logger.Error(exception, "API Error");
}
await httpContext.Response.WriteAsync(JsonConvert.SerializeObject(new Error(statusCode, httpContext.Request.CorrelationId(), exception.Message, statusCode.ToString())));
}
}
The Error class looks like this:
public class Error
{
public int Code { get; }
public Guid? CorrelationId { get; }
public DateTime DateUtc { get; }
public string ErrorMessage { get; }
public string ErrorType { get; }
public Error(HttpStatusCode code, Guid? correlationId, string errorMessage, string errorType)
{
Code = (int)code;
CorrelationId = correlationId;
DateUtc = DateTime.UtcNow;
ErrorMessage = errorMessage;
ErrorType = errorType;
}
}
I created this class:
public class ApiCallException : Exception
{
public int StatusCode { get; }
public override string Message { get; }
public ApiCallException(int statusCode, string message)
{
StatusCode = statusCode;
Message = message;
}
}
Then updated my original code to have this:
if (!response.IsSuccessStatusCode)
{
throw new ApiCallException((int)response.StatusCode, await response.Content.ReadAsStringAsync());
}

ASP.NET MVC: Why my custom ActionFilter changes my HTTP response code?

I've developed a custom action filter in order to use it for logging response of my web-service in ASP.NET MVC.
However I don't know why when I add this action filter to my method, HTTP status response of my controller changes to 500 and it returns the message: 500 Intenal Server Error. I put all logic inside try catch block but still problem persists.
Here is my custom ActionFilter:
public class LogActionFilter : System.Web.Http.Filters.ActionFilterAttribute
{
public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
{
base.OnActionExecuted(actionExecutedContext);
try
{
Log("OnActionExecuting", actionExecutedContext);
}
catch (Exception)
{
}
}
private void Log(string methodName, HttpActionExecutedContext context)
{
try
{
string resopnseBody = getBodyFromResponse(context);
HttpResponseMessage response = context.Response;
var headers = response.Headers;
var content = response.Content;
var actionName = response.ToString();
var message = "";
message = String.Format("response:{0}", resopnseBody);
Debug.WriteLine(message, "");
}
catch (Exception e)
{
}
}
private string getBodyFromResponse(HttpActionExecutedContext context)
{
string data;
using (var stream = context.Response.Content.ReadAsStreamAsync().Result)
{
if (stream.CanSeek)
{
stream.Position = 0;
}
data = context.Response.Content.ReadAsStringAsync().Result;
}
return data;
}
}
Update:
Furthur investigating my code I found that calling getBodyFromResponse leads to this error. I myself suspect to part which I will try to read stream .Result twice however since I copied! this code from elsewhere I don't understand its logic clearly.
Update2:
Here is a sample method in my controller:
[LogActionFilter]
[System.Web.Http.HttpPost]
public async Task<IHttpActionResult> Test()
{
return Ok(new WebServiceResult { responseCode = 0, responseMessage = null });
}
Update 3:
replacing
resopnseBody = getBodyFromResponse(context);
with below line fixed issue but I don't know why!
resopnseBody = context.Response.Content.ReadAsStringAsync().Result;

I got it to run by removing some lines from getBodyFromResponseAsync
private string getBodyFromResponseAsync(HttpActionExecutedContext context)
{
return context.Response.Content.ReadAsStringAsync().Result;
}
I hope the result is what you need.

Wrapping all responses

I want to wrap all my http responses.
For example we have an action which returns some JSON data:
public IActionResult Get()
{
var res = new
{
MessageBody = "Test",
SomeData = 1
};
return Ok(res);
}
I want my response looks like:
{
"StatusCode":200,
"Result":
{
"MessageBody ":"Test",
"SomeData":1
}
}
If there is error then response must contain ErrorMessage field in a response.
In the mvc 5 I used the DelegationHandler, but in the asp.net core this class is not implemented. Now, we have to use middlewares.
This is code for mvc 5:
public class WrappingHandler : DelegatingHandler
{
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
var response = await base.SendAsync(request, cancellationToken);
return BuildApiResponse(request, response);
}
private static HttpResponseMessage BuildApiResponse(HttpRequestMessage request, HttpResponseMessage response)
{
object content;
string errorMessage = null;
if (response.TryGetContentValue(out content) && !response.IsSuccessStatusCode)
{
HttpError error = content as HttpError;
if (error != null)
{
content = null;
errorMessage = error.Message;
#if DEBUG
errorMessage = string.Concat(errorMessage, error.ExceptionMessage, error.StackTrace);
#endif
}
}
var newResponse = request.CreateResponse(response.StatusCode, new ApiResponse(response.StatusCode, content, errorMessage));
foreach (var header in response.Headers)
{
newResponse.Headers.Add(header.Key, header.Value);
}
return newResponse;
}
}
and, a middleware for asp.net core. There are no TryGetContentValue, HttpError and other stuff in asp.net core. So, I am trying to read response body first:
public class FormatApiResponseMiddleware
{
private readonly RequestDelegate _next;
public FormatApiResponseMiddleware(RequestDelegate next)
{
_next = next;
}
private bool IsSuccessStatusCode(int statusCode)
{
return (statusCode >= 200) && (statusCode <= 299);
}
public async Task Invoke(HttpContext context)
{
object content = null;
string errorMessage = null;
if (!IsSuccessStatusCode(context.Response.StatusCode))
{
content = null;
//how to get error
}
var body= context.Response.Body;
}
}
But, Body stream has CanRead equal false and I get error that stream cannot be read. How to properly wrap response?

I suggest using ExceptionHandlerMiddleware as a template/sample on how your middleware should be implemented.
For example, you should be aware about case, when response has already started
// We can't do anything if the response has already started, just abort.
if (context.Response.HasStarted)
{
_logger.LogWarning("The response has already started, the error handler will not be executed.");
throw;
}
or don't forget to clear current response, if you want to replace it:
context.Response.Clear();
Moreover, maybe you will find useful just to reuse it, and implement your own error handler instead of a full middleware. That way you can send a custom JSON error to the client. For that, define a class that will represent your custom error:
public class ErrorDto
{
public int Code { get; set; }
public string Message { get; set; }
// other fields
public override string ToString()
{
return JsonConvert.SerializeObject(this);
}
}
Then register an exception handler middleware in the Configure method. Pay attention to the order in which the middleware is registered, and make sure it’s registered before MVC for example:
app.UseExceptionHandler(errorApp =>
{
errorApp.Run(async context =>
{
context.Response.StatusCode = 500; // or another Status
context.Response.ContentType = "application/json";
var error = context.Features.Get<IExceptionHandlerFeature>();
if (error != null)
{
var ex = error.Error;
await context.Response.WriteAsync(new ErrorDto()
{
Code = 1, //<your custom code based on Exception Type>,
Message = ex.Message // or your custom message
// … other custom data
}.ToString(), Encoding.UTF8);
}
});
});

Error handling (Sending ex.Message to the client)

I have an ASP.NET Core 1.0 Web API application and trying to figure out how to pass the exception message to the client if a function that my controller is calling errors out.
I have tried so many things, but nothing implements IActionResult.
I don't understand why this isn't a common thing that people need. If there truthfully is no solution can someone tell me why?
I do see some documentation out there using HttpResponseException(HttpResponseMessage), but in order to use this, I have to install the compat shim. Is there a new way of doing these things in Core 1.0?
Here is something I have been trying with the shim but it isn't working:
// GET: api/customers/{id}
[HttpGet("{id}", Name = "GetCustomer")]
public IActionResult GetById(int id)
{
Customer c = _customersService.GetCustomerById(id);
if (c == null)
{
var response = new HttpResponseMessage(HttpStatusCode.NotFound)
{
Content = new StringContent("Customer doesn't exist", System.Text.Encoding.UTF8, "text/plain"),
StatusCode = HttpStatusCode.NotFound
};
throw new HttpResponseException(response);
//return NotFound();
}
return new ObjectResult(c);
}
When the HttpResponseException is thrown, I look on the client and can't find the message I am sending anything in the content.

Here is an simple error DTO class
public class ErrorDto
{
public int Code {get;set;}
public string Message { get; set; }
// other fields
public override string ToString()
{
return JsonConvert.SerializeObject(this);
}
}
And then using the ExceptionHandler middleware:
app.UseExceptionHandler(errorApp =>
{
errorApp.Run(async context =>
{
context.Response.StatusCode = 500; // or another Status accordingly to Exception Type
context.Response.ContentType = "application/json";
var error = context.Features.Get<IExceptionHandlerFeature>();
if (error != null)
{
var ex = error.Error;
await context.Response.WriteAsync(new ErrorDto()
{
Code = <your custom code based on Exception Type>,
Message = ex.Message // or your custom message
// other custom data
}.ToString(), Encoding.UTF8);
}
});
});

Yes it is possible to change the status code to whatever you need:
In your CustomExceptionFilterAttribute.cs file modify the code as follows:
public class CustomExceptionFilterAttribute : ExceptionFilterAttribute
{
public override void OnException(ExceptionContext context)
{
var exception = context.Exception;
context.Result = new ContentResult
{
Content = $"Error: {exception.Message}",
ContentType = "text/plain",
// change to whatever status code you want to send out
StatusCode = (int?)HttpStatusCode.BadRequest
};
}
}
That's pretty much it.
If you have custom exceptions, then you can also check for them when grabbing the thrown exception from the context. Following on from that you can then send out different HTTP Status Codes depdending on what has happened in your code.
Hope that helps.

You can create a custom Exception Filter like below
public class CustomExceptionFilterAttribute : ExceptionFilterAttribute
{
public override void OnException(ExceptionContext context)
{
var exception = context.Exception;
context.Result = new JsonResult(exception.Message);
}
}
Then apply the above attribute to your controller.
[Route("api/[controller]")]
[CustomExceptionFilter]
public class ValuesController : Controller
{
// GET: api/values
[HttpGet]
public IEnumerable<string> Get()
{
throw new Exception("Suckers");
return new string[] { "value1", "value2" };
}
}

Rather than raising and catching an exception, how about you simplify your action to:
// GET: api/customers/{id}
[HttpGet("{id}", Name = "GetCustomer")]
public IActionResult GetById(int id)
{
var customer = _customersService.GetCustomerById(id);
if (customer == null)
{
return NotFound("Customer doesn't exist");
}
return Ok(customer);
}
I wrote a blog post with some more options such as returning a JSON object instead of text.

Maybe that is helpful. You can return just object and sent for example a BadRequest (HTTP CODE: 400) with your custom object as actual parameter (I just used an interpolated string here) but you can put in anything.
In your client side you can catch that error situation for example with an AJAX error handler.
// GET: api/TruckFahrerGeoData
[HttpGet]
public object GetTruckFahrerGeoData()
{
var truckFahrerGeoDataItems = new List<TruckFahrerGeoDataViewModel>();
var geodataItems = _context.TruckFahrerGeoData;
foreach (var truckFahrerGeoData in geodataItems)
{
GeoTelemetryData geoTelemetryData = JsonConvert.DeserializeObject<GeoTelemetryData>(truckFahrerGeoData.TelemetryData);
if (geoTelemetryData == null)
{
return BadRequest($"geoTelemetryData null for id: {truckFahrerGeoData.Id}");
}
TruckFahrerGeoDataViewModel truckFahrerGeoDataViewModel = new TruckFahrerGeoDataViewModel
{
Speed = geoTelemetryData.Speed,
Accuracy = geoTelemetryData.Accuracy,
TruckAppId = geoTelemetryData.Activity.TruckAppId,
TruckAuftragStatusId = geoTelemetryData.Activity.TruckAuftragStatusId,
ClId = geoTelemetryData.Activity.ClId,
TruckAuftragLaufStatusId = geoTelemetryData.Activity.TruckAuftragLaufStatusId,
TaskId = geoTelemetryData.Activity.TaskId,
TruckAuftragWorkflowStatusId = geoTelemetryData.Activity.TruckAuftragWorkflowStatusId
};
truckFahrerGeoDataItems.Add(truckFahrerGeoDataViewModel);
}
return truckFahrerGeoDataItems;
}
Or an even more cleaner way with IActionResult like that way:
// GET: api/TruckFahrerGeoData
[HttpGet]
public IActionResult GetTruckFahrerGeoData()
{
var truckFahrerGeoDataItems = new List<TruckFahrerGeoDataViewModel>();
var geodataItems = _context.TruckFahrerGeoData;
foreach (var truckFahrerGeoData in geodataItems)
{
GeoTelemetryData geoTelemetryData = JsonConvert.DeserializeObject<GeoTelemetryData>(truckFahrerGeoData.TelemetryData);
if (geoTelemetryData == null)
{
return BadRequest($"geoTelemetryData null for id: {truckFahrerGeoData.Id}");
}
TruckFahrerGeoDataViewModel truckFahrerGeoDataViewModel = new TruckFahrerGeoDataViewModel
{
Speed = geoTelemetryData.Speed,
Accuracy = geoTelemetryData.Accuracy,
TruckAppId = geoTelemetryData.Activity.TruckAppId,
TruckAuftragStatusId = geoTelemetryData.Activity.TruckAuftragStatusId,
ClId = geoTelemetryData.Activity.ClId,
TruckAuftragLaufStatusId = geoTelemetryData.Activity.TruckAuftragLaufStatusId,
TaskId = geoTelemetryData.Activity.TaskId,
TruckAuftragWorkflowStatusId = geoTelemetryData.Activity.TruckAuftragWorkflowStatusId
};
truckFahrerGeoDataItems.Add(truckFahrerGeoDataViewModel);
}
return Ok(truckFahrerGeoDataItems);
}

Late to the party but refining the answer .
Define your error response class with minimum below attributes
using Microsoft.AspNetCore.Http;
public class ErrorResponse
{
private readonly RequestDelegate next;
public ErrorResponse(RequestDelegate next)
{
this.next = next;
}
public async Task Invoke(HttpContext context )
{
try
{
await next(context);
}
catch (Exception ex)
{
await HandleExceptionAsync(context, ex);
}
}
private static Task HandleExceptionAsync(HttpContext context, Exception ex)
{
var code = HttpStatusCode.InternalServerError;
string result = string.Empty;
object data = new object();
if (ex is ForbiddenException)
{
code = HttpStatusCode.Forbidden;
result = JsonConvert.SerializeObject(new Response<object>(Status.Forbidden(ex.Message), data));
}
else if(ex is BadRequestException){
code = HttpStatusCode.BadRequest;
result = JsonConvert.SerializeObject(new Response<object>(Status.BadRequest(ex.Message), data));
}
else if (ex is NotFoundException)
{
code = HttpStatusCode.NotFound;
result = JsonConvert.SerializeObject(new Response<object>(Status.NotFound(ex.Message), data));
}
else if (ex is UnauthorizedException)
{
code = HttpStatusCode.Unauthorized;
result = JsonConvert.SerializeObject(new Response<object>(Status.Unauthorized(ex.Message), data));
}
else
{
result = JsonConvert.SerializeObject(new Response<object>(Status.InternalServerError(ex.Message), data));
}
context.Response.ContentType = "application/json";
context.Response.StatusCode = (int)code;
return context.Response.WriteAsync(result);
}
}
Next use this class as middleware in startup.cs class
app.UseHttpsRedirection();
app.UseMiddleware(typeof(ErrorResponse));
Now each request and response will go through this class,if an error occurs then error code will be set to true with error code. A sample response like below
data: {}
status: {
code: 404
error: true
message: "No employee data found"
type: "Not Found"
}

I had the same problem and after some research, I found out I could use HttpClient to call my API and read the response easily. HttpClient does not throw any error when the HTTP response contains an error code, but it sets the IsSuccessStatusCode property to false.
This is my function using the HttpClient. I call this from my controller.
public static async Task<HttpResponseMessage> HttpClientPost(string header, string postdata, string url)
{
string uri = apiUrl + url;
using (var client = new HttpClient())
{
//client.BaseAddress = new Uri(uri);
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", header);
HttpResponseMessage response = await client.PostAsync(uri, new StringContent(postdata));
return response;
}
}
This is my controller code, where I call the function and read the response and determine whether I have an error or not and respond accordingly. Note that I am checking the IsSuccessStatusCode.
HttpResponseMessage response;
string url = $"Setup/AddDonor";
var postdata = JsonConvert.SerializeObject(donor);
response = await ApiHandler.HttpClientPost(HttpContext.Session.GetString(tokenName), postdata, url);
//var headers = response.Headers.Concat(response.Content.Headers);
var responseBody = await response.Content.ReadAsStringAsync();
if (response.IsSuccessStatusCode)
{
tnxresult = JsonConvert.DeserializeObject<TnxResult>(AppFunctions.CleanResponse(responseBody));
return Json(new
{
ok = true,
message = tnxresult.Message,
statusCode = tnxresult.StatusCode
});
}
else
{
ApiError rs = JsonConvert.DeserializeObject<ApiError>(AppFunctions.CleanResponse(responseBody));
return Json(new
{
ok = false,
message = rs.Message,
statusCode = rs.StatusCode
});
}
My API returns error messages in JSON. If the call is successful, I am packing the response in JSON too.
The crucial line of code is this one...
var responseBody = await response.Content.ReadAsStringAsync();
It serializes the HTTP content to a string as an asynchronous operation.
After that I can convert my JSON string to an object and access the error/success message and the Status Code too.

Return JSON with error status code MVC

I was trying to return an error to the call to the controller as advised in
This link so that client can take appropriate action.
The controller is called by javascript via jquery AJAX. I am getting the Json object back only if I don't set the status to error.
Here is the sample code
if (response.errors.Length > 0)
Response.StatusCode = (int)HttpStatusCode.BadRequest;
return Json(response);
I get the Json if I don't set the statuscode.
If I set the status code I get the status code back but not the Json error object.
Update
I want to send an Error object as JSON so that it can be handled error callback of ajax.

The neatest solution I've found is to create your own JsonResult that extends the original implementation and allows you to specify a HttpStatusCode:
public class JsonHttpStatusResult : JsonResult
{
private readonly HttpStatusCode _httpStatus;
public JsonHttpStatusResult(object data, HttpStatusCode httpStatus)
{
Data = data;
_httpStatus = httpStatus;
}
public override void ExecuteResult(ControllerContext context)
{
context.RequestContext.HttpContext.Response.StatusCode = (int)_httpStatus;
base.ExecuteResult(context);
}
}
You can then use this in your controller action like so:
if(thereWereErrors)
{
var errorModel = new { error = "There was an error" };
return new JsonHttpStatusResult(errorModel, HttpStatusCode.InternalServerError);
}

I found the solution here
I had to create a action filter to override the default behaviour of MVC
Here is my exception class
class ValidationException : ApplicationException
{
public JsonResult exceptionDetails;
public ValidationException(JsonResult exceptionDetails)
{
this.exceptionDetails = exceptionDetails;
}
public ValidationException(string message) : base(message) { }
public ValidationException(string message, Exception inner) : base(message, inner) { }
protected ValidationException(
System.Runtime.Serialization.SerializationInfo info,
System.Runtime.Serialization.StreamingContext context)
: base(info, context) { }
}
Note that I have constructor which initializes my JSON. Here is the action filter
public class HandleUIExceptionAttribute : FilterAttribute, IExceptionFilter
{
public virtual void OnException(ExceptionContext filterContext)
{
if (filterContext == null)
{
throw new ArgumentNullException("filterContext");
}
if (filterContext.Exception != null)
{
filterContext.ExceptionHandled = true;
filterContext.HttpContext.Response.Clear();
filterContext.HttpContext.Response.TrySkipIisCustomErrors = true;
filterContext.HttpContext.Response.StatusCode = (int)System.Net.HttpStatusCode.InternalServerError;
filterContext.Result = ((ValidationException)filterContext.Exception).myJsonError;
}
}
Now that I have the action filter, I will decorate my controller with the filter attribute
[HandleUIException]
public JsonResult UpdateName(string objectToUpdate)
{
var response = myClient.ValidateObject(objectToUpdate);
if (response.errors.Length > 0)
throw new ValidationException(Json(response));
}
When the error is thrown the action filter which implements IExceptionFilter get called and I get back the Json on the client on error callback.

There is a very elegant solution to this problem, just configure your site via web.config:
<system.webServer>
<httpErrors errorMode="DetailedLocalOnly" existingResponse="PassThrough"/>
</system.webServer>
Source: https://serverfault.com/questions/123729/iis-is-overriding-my-response-content-if-i-manually-set-the-response-statuscode

A simple way to send a error to Json is control Http Status Code of response object and set a custom error message.
Controller
public JsonResult Create(MyObject myObject)
{
//AllFine
return Json(new { IsCreated = True, Content = ViewGenerator(myObject));
//Use input may be wrong but nothing crashed
return Json(new { IsCreated = False, Content = ViewGenerator(myObject));
//Error
Response.StatusCode = (int)HttpStatusCode.InternalServerError;
return Json(new { IsCreated = false, ErrorMessage = 'My error message');
}
JS
$.ajax({
type: "POST",
dataType: "json",
url: "MyController/Create",
data: JSON.stringify(myObject),
success: function (result) {
if(result.IsCreated)
{
//... ALL FINE
}
else
{
//... Use input may be wrong but nothing crashed
}
},
error: function (error) {
alert("Error:" + erro.responseJSON.ErrorMessage ); //Error
}
});

Building on the answer from Richard Garside, here's the ASP.Net Core version
public class JsonErrorResult : JsonResult
{
private readonly HttpStatusCode _statusCode;
public JsonErrorResult(object json) : this(json, HttpStatusCode.InternalServerError)
{
}
public JsonErrorResult(object json, HttpStatusCode statusCode) : base(json)
{
_statusCode = statusCode;
}
public override void ExecuteResult(ActionContext context)
{
context.HttpContext.Response.StatusCode = (int)_statusCode;
base.ExecuteResult(context);
}
public override Task ExecuteResultAsync(ActionContext context)
{
context.HttpContext.Response.StatusCode = (int)_statusCode;
return base.ExecuteResultAsync(context);
}
}
Then in your controller, return as follows:
// Set a json object to return. The status code defaults to 500
return new JsonErrorResult(new { message = "Sorry, an internal error occurred."});
// Or you can override the status code
return new JsonErrorResult(new { foo = "bar"}, HttpStatusCode.NotFound);

The thing that worked for me (and that I took from another stackoverflow response), is to set the flag:
Response.TrySkipIisCustomErrors = true;

You have to return JSON error object yourself after setting the StatusCode, like so ...
if (BadRequest)
{
Dictionary<string, object> error = new Dictionary<string, object>();
error.Add("ErrorCode", -1);
error.Add("ErrorMessage", "Something really bad happened");
return Json(error);
}
Another way is to have a JsonErrorModel and populate it
public class JsonErrorModel
{
public int ErrorCode { get; set;}
public string ErrorMessage { get; set; }
}
public ActionResult SomeMethod()
{
if (BadRequest)
{
var error = new JsonErrorModel
{
ErrorCode = -1,
ErrorMessage = "Something really bad happened"
};
return Json(error);
}
//Return valid response
}
Take a look at the answer here as well

You need to decide if you want "HTTP level error" (that what error codes are for) or "application level error" (that what your custom JSON response is for).
Most high level objects using HTTP will never look into response stream if error code set to something that is not 2xx (success range). In your case you are explicitly setting error code to failure (I think 403 or 500) and force XMLHttp object to ignore body of the response.
To fix - either handle error conditions on client side or not set error code and return JSON with error information (see Sbossb reply for details).

Several of the responses rely on an exception being thrown and having it handled in the OnException override. In my case, I wanted to return statuses such as bad request if the user, say, had passed in a bad ID. What works for me is to use the ControllerContext:
var jsonResult = new JsonResult { JsonRequestBehavior = JsonRequestBehavior.AllowGet, Data = "whoops" };
ControllerContext.HttpContext.Response.StatusCode = (int)HttpStatusCode.BadRequest;
return jsonResult;

And if your needs aren't as complex as Sarath's you can get away with something even simpler:
[MyError]
public JsonResult Error(string objectToUpdate)
{
throw new Exception("ERROR!");
}
public class MyErrorAttribute : FilterAttribute, IExceptionFilter
{
public virtual void OnException(ExceptionContext filterContext)
{
if (filterContext == null)
{
throw new ArgumentNullException("filterContext");
}
if (filterContext.Exception != null)
{
filterContext.ExceptionHandled = true;
filterContext.HttpContext.Response.Clear();
filterContext.HttpContext.Response.TrySkipIisCustomErrors = true;
filterContext.HttpContext.Response.StatusCode = (int)System.Net.HttpStatusCode.InternalServerError;
filterContext.Result = new JsonResult() { Data = filterContext.Exception.Message };
}
}
}

If you are just using MVC the simplest way is to use HttpStatusCodeResult.
public ActionResult MyAjaxRequest(string args)
{
string error_message = string.Empty;
try
{
// successful
return Json(args);
}
catch (Exception e)
{
error_message = e.Message;
}
return new HttpStatusCodeResult(500, error_message);
}
When the error is returned to the client you can display it or action it how you like.
request.fail(function (jqXHR) {
if (jqXHR.status == 500) {
alert(jqXHR.statusText);
}
})

I was running Asp.Net Web Api 5.2.7 and it looks like the JsonResult class has changed to use generics and an asynchronous execute method. I ended up altering Richard Garside's solution:
public class JsonHttpStatusResult<T> : JsonResult<T>
{
private readonly HttpStatusCode _httpStatus;
public JsonHttpStatusResult(T content, JsonSerializerSettings serializer, Encoding encoding, ApiController controller, HttpStatusCode httpStatus)
: base(content, serializer, encoding, controller)
{
_httpStatus = httpStatus;
}
public override Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
var returnTask = base.ExecuteAsync(cancellationToken);
returnTask.Result.StatusCode = HttpStatusCode.BadRequest;
return returnTask;
}
}
Following Richard's example, you could then use this class like this:
if(thereWereErrors)
{
var errorModel = new CustomErrorModel("There was an error");
return new JsonHttpStatusResult<CustomErrorModel>(errorModel, new JsonSerializerSettings(), new UTF8Encoding(), this, HttpStatusCode.InternalServerError);
}
Unfortunately, you can't use an anonymous type for the content, as you need to pass a concrete type (ex: CustomErrorType) to the JsonHttpStatusResult initializer. If you want to use anonymous types, or you just want to be really slick, you can build on this solution by subclassing ApiController to add an HttpStatusCode param to the Json methods :)
public abstract class MyApiController : ApiController
{
protected internal virtual JsonHttpStatusResult<T> Json<T>(T content, HttpStatusCode httpStatus, JsonSerializerSettings serializerSettings, Encoding encoding)
{
return new JsonHttpStatusResult<T>(content, httpStatus, serializerSettings, encoding, this);
}
protected internal JsonHttpStatusResult<T> Json<T>(T content, HttpStatusCode httpStatus, JsonSerializerSettings serializerSettings)
{
return Json(content, httpStatus, serializerSettings, new UTF8Encoding());
}
protected internal JsonHttpStatusResult<T> Json<T>(T content, HttpStatusCode httpStatus)
{
return Json(content, httpStatus, new JsonSerializerSettings());
}
}
Then you can use it with an anonymous type like this:
if(thereWereErrors)
{
var errorModel = new { error = "There was an error" };
return Json(errorModel, HttpStatusCode.InternalServerError);
}

Here is the JsonResult override answer for ASP.NET v5+ . I have tested and it works just as well as in earlier versions.
public class JsonHttpStatusResult : JsonResult
{
private readonly HttpStatusCode _httpStatus;
public JsonHttpStatusResult(object data, HttpStatusCode httpStatus) : base(data)
{
_httpStatus = httpStatus;
}
public override Task ExecuteResultAsync(ActionContext context)
{
context.HttpContext.Response.StatusCode = (int)_httpStatus;
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
var services = context.HttpContext.RequestServices;
var executor = services.GetRequiredService<IActionResultExecutor<JsonResult>>();
return executor.ExecuteAsync(context, this);
}
}