I have two projects in one solution. The 1st it's library project and the second it's Asp.Net WebApi project. Both using .Net Framework 4.6.1.
I want to make some class that will handling exceptions globally. I found nice solution using ExceptionHandler, however it doesn't work as I expected. I was following this article https://learn.microsoft.com/pl-pl/aspnet/web-api/overview/error-handling/web-api-global-error-handling.
Here is my class where I handle exceptions.
public class GlobalExceptionHandler : ExceptionHandler
{
public override void HandleCore(ExceptionHandlerContext context)
{
context.Result = new TextPlainErrorResult
{
Request = context.ExceptionContext.Request,
Content = context.Exception.Message
};
}
private class TextPlainErrorResult : IHttpActionResult
{
public HttpRequestMessage Request { get; set; }
public string Content { get; set; }
public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
HttpResponseMessage response =
new HttpResponseMessage(HttpStatusCode.InternalServerError);
response.Content = new StringContent(Content);
response.RequestMessage = Request;
return Task.FromResult(response);
}
}
}
For instance I have this code in my library project.
public class ThrowSomething
{
public void ThrowSomeException()
{
throw new Exception("Custom exception");
}
}
And in my controller in Asp.Net I have
public IHttpActionResult SomeAction()
{
var throwSomething = new ThrowSomething();
throwSomething.ThrowSomeException();
return Ok();
}
I would like to catch the exception in my GlobalExceptionHandler class and return some result to the Api. Currently the GlobalExceptionHandler is not handling the exceptions.
I also have config.Services.Replace(typeof(IExceptionHandler), new GlobalExceptionHandler()); in Register method in WebApiConfig.
in my webapi project I have a global exception handler and I want to set the status code 500 when an exception is uncaught and I want to set a custom message, but I don't know how to set that message. Here is my code:
public class MyExceptionHandler : IExceptionHandler
{
public Task HandleAsync(ExceptionHandlerContext context, CancellationToken cancellationToken)
{
context.Result = new StatusCodeResult(HttpStatusCode.InternalServerError, context.Request);
return Task.FromResult<object>(null);
}
}
and the config is:
config.IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.LocalOnly;
config.Services.Replace(typeof(IExceptionHandler), new MyExceptionHandler());
In postman the response body is empty and I just see the 500 error code. So how to set a message here?
Here is an example:
public class ExceptionFilter : ExceptionFilterAttribute
{
private TelemetryClient TelemetryClient { get; }
public ExceptionFilter(TelemetryClient telemetryClient)
{
TelemetryClient = telemetryClient;
}
public override void OnException(ExceptionContext context)
{
context.ExceptionHandled = true;
context.HttpContext.Response.Clear();
context.HttpContext.Response.StatusCode = (int) HttpStatusCode.InternalServerError;
context.Result = new JsonResult(new
{
error = context.Exception.Message
});
TelemetryClient.TrackException(context.Exception);
}
}
and you can use it in your startup - ConfigureService:
services.AddSingleton<ExceptionFilter>();
services.AddMvc(
options => { options.Filters.Add(services.BuildServiceProvider().GetService<ExceptionFilter>()); });
it will now also send exception to azure telemetry.
You can offcourse remove the telemetryclient and the methods :)
cheers!
When ovveride the IExceptionHandler, the response does not reach the DelegatingHandler when a unexpected exception occurs. How can I fix this?
In webapi 2, I want to implement a audit logger for request and response messages. I also want to add a global exception handler. However, when I replace the IExceptionHandler with my custom implementation. the response never reaches the DelegatingHandler -on exception - And thus the audit for response is lost.
in WebApiConfig
// add custom audittrail logger
config.MessageHandlers.Add(new AuditLogHandler());
// replace global exception handeling
config.Services.Replace(typeof(IExceptionHandler), new WebAPiExceptionHandler());
Custom Exception Handler
public class WebAPiExceptionHandler : ExceptionHandler
{
//A basic DTO to return back to the caller with data about the error
private class ErrorInformation
{
public string Message { get; set; }
public DateTime ErrorDate { get; set; }
}
public override void Handle(ExceptionHandlerContext context)
{
context.Result = new ResponseMessageResult(context.Request.CreateResponse(HttpStatusCode.InternalServerError,
new ErrorInformation { Message = "Iets is misgegaan", ErrorDate = DateTime.UtcNow }));
}
}
Custom Auditlogger
public class AuditLogHandler : DelegatingHandler
{
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
if (request.Content != null)
{
var task = await request.Content.ReadAsStringAsync();
// .. code for loggign request
}
var result = await base.SendAsync(request, cancellationToken);
// .. code for logging response
// when I do not replace WebAPiExceptionHandler, code is reachred here
// When I Do use WebAPiExceptionHandler, code is not reached here
return result;
}
}
Code for throwing exception in webapi
public class Values_v2Controller : ApiController
{
public string Get(int id)
{
throw new Exception("haha");
}
}
Dont use ExceptionHandler as base class, implement interface IExceptionHandler
public class WebAPiExceptionHandler : IExceptionHandler
{
public Task HandleAsync(ExceptionHandlerContext context, CancellationToken cancellationToken)
{
var fout = new ErrorInformation
{
Message = "Iets is misgegaan"
, ErrorDate = DateTime.UtcNow
};
var httpResponse = context.Request.CreateResponse(HttpStatusCode.InternalServerError, fout);
context.Result = new ResponseMessageResult(httpResponse);
return Task.FromResult(0);
}
private class ErrorInformation
{
public string Message { get; set; }
public DateTime ErrorDate { get; set; }
}
}
The problem is that ExceptionHandler only executes Handle(ExceptionHandlerContext context) method if ShouldHandle(ExceptionHandlerContext context) returns true.
Overriding bool ShouldHandle(ExceptionHandlerContext context) to always return true fix the problem for me.
I was wondering if it was possible to set some custom header values whenever an internal server error has occurred? I am currently doing:
public class FooExceptionHandler : ExceptionHandler
{
public override void Handle(ExceptionHandlerContext context)
{
// context.Result already contains my custom header values
context.Result = new InternalServerErrorResult(context.Request);
}
}
Here I also want to set some header values but though it appears in the request the response does not contain it.
Is there a way of doing this?
There is a sample code for your reference, my ApiExceptionHandler is your
FooExceptionHandler
public class ApiExceptionHandler : ExceptionHandler
{
public override void Handle(ExceptionHandlerContext context)
{
var response = new Response<string>
{
Code = StatusCode.Exception,
Message = $#"{context.Exception.Message},{context.Exception.StackTrace}"
};
context.Result = new CustomeErrorResult
{
Request = context.ExceptionContext.Request,
Content = JsonConvert.SerializeObject(response),
};
}
}
internal class CustomeErrorResult : IHttpActionResult
{
public HttpRequestMessage Request { get; set; }
public string Content { get; set; }
public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
var response =
new HttpResponseMessage(HttpStatusCode.InternalServerError)
{
Content = new StringContent(Content),
RequestMessage = Request
};
response.Headers.Add("Access-Control-Allow-Origin", "*");
response.Headers.Add("Access-Control-Allow-Headers", "*");
return Task.FromResult(response);
}
}
It should be possible by creating your own exception filter.
namespace MyApplication.Filters
{
using System;
using System.Net;
using System.Net.Http;
using System.Web.Http.Filters;
public class CustomHeadersFilterAttribute : ExceptionFilterAttribute
{
public override void OnException(HttpActionExecutedContext context)
{
context.Response.Content.Headers.Add("X-CustomHeader", "whatever...");
}
}
}
http://www.asp.net/web-api/overview/error-handling/exception-handling
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);
}
}