I am trying to create a simple web API.
I have data going into the controller but I can't return it in the JSON API. I think the problem is returning the IEnumerable String.
BLL:
public IEnumerable<DTO.Gettod> Gettods()
{
DAL.todDataController tdc = new DAL.todDataController();
return tdc.GetToddMobiles();
}
Model:
public class TodViewModel
{
public IEnumerable<DTO.Gettod> ModelGetTod { get; set; }
}
Controller:
public IEnumerable<string> Get()
{
BLL.todManager tm = new BLL.todManager();
Models.TodViewModel tvm = new Models.TodViewModel();
tvm.ModelGetTod = tm.Gettods().ToArray();
return tvm as IEnumerable<string>;
}
JSON file returns only a Null but I'm expecting an Array.
The Correct Code is below, crediting: Bruno in the below answer:
public IHttpActionResult GetToddData()
{
BLL.todManager tm = new BLL.todManager();
Models.TodViewModel tvm = new Models.TodViewModel();
tvm.ModelGetTod = tm.Gettods().ToList();
//HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.OK, tvm.ModelGetTod as IEnumerable<string>);
return Ok(tvm.ModelGetTod);
}
Try changing your controller to the below:
Edit: Changing the accepted answer to what worked for the user
public IHttpActionResult GetToddData () {
BLL.todManager tm = new BLL.todManager ();
Models.TodViewModel tvm = new Models.TodViewModel ();
tvm.ModelGetTod = tm.Gettods ().ToList ();
//HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.OK, tvm.ModelGetTod as IEnumerable<string>);
return Ok (tvm.ModelGetTod);
}
Also, debug and see if you are getting the expected values in the tvm.ModelGetTod property.
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);
}
}
I am trying to understand custom exceptionhandlers but am not getting the hang of it. I tried implementing a custom exception handler like explained in the following pages:
https://www.exceptionnotfound.net/the-asp-net-web-api-exception-handling-pipeline-a-guided-tour/
https://learn.microsoft.com/en-us/aspnet/web-api/overview/error-handling/web-api-global-error-handling
Now my code is:
public class CustomRestErrorHandlerException : ExceptionHandler
{
public void CustomError(String error)
{
var message = new HttpResponseMessage(HttpStatusCode.NoContent)
{
Content = new StringContent("An unknown error occurred saying" + error)
};
throw new HttpResponseException(message);
}
public override void Handle(ExceptionHandlerContext context)
{
if (context.Exception is ArgumentNullException)
{
var result = new HttpResponseMessage(HttpStatusCode.BadRequest)
{
Content = new StringContent(context.Exception.Message),
ReasonPhrase = "ArgumentNullException"
};
context.Result = new ErrorMessageResult(context.Request, result);
}
else if (context.Exception is ArgumentException)
{
var result = new HttpResponseMessage(HttpStatusCode.NoContent)
{
Content = new StringContent(context.Exception.Message),
ReasonPhrase = "Argument is not found"
};
context.Result = new ErrorMessageResult(context.Request, result);
}
else if (context.Exception is ArgumentOutOfRangeException)
{
var result = new HttpResponseMessage(HttpStatusCode.NotImplemented)
{
Content = new StringContent(context.Exception.Message),
ReasonPhrase = "Argument is out of range"
};
context.Result = new ErrorMessageResult(context.Request, result);
}
else
{
CustomError(context.Exception.Message);
}
}
public class ErrorMessageResult : IHttpActionResult
{
private HttpRequestMessage _request;
private HttpResponseMessage _httpResponseMessage;
public ErrorMessageResult(HttpRequestMessage request, HttpResponseMessage httpResponseMessage)
{
_request = request;
_httpResponseMessage = httpResponseMessage;
}
public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
return Task.FromResult(_httpResponseMessage);
}
}
}
Then I try to call the exceptionhandler which I obviously do wrong : (this I probably do not understand <<
[Route("api/***/***")]
[HttpGet]
public IHttpActionResult Clear****()
{
try
{
// try clearing
}
catch(Exception e)
{
throw new CustomRestErrorHandlerException(); << error occurs here
}
return this.Ok();
}
As you can see the error occurs because the exception is not an exceptionhandler but I have no idea how to then throw an exception through an custom exception handler since it's explained nowhere.
Can anyone explain this to me with a small example perhaps?
ExceptionHandler's have to be registered in the Web API configuration. This can be done in the WebApiConfig.cs file as shown below, where config is of type System.Web.Http.HttpConfiguration.
config.Services.Replace(typeof(IExceptionHandler), new GlobalExceptionHandler());
Once they are registered they are automatically called during unhandled exceptions. To test it out you might want to throw an exception in the action method such as:
[Route("api/***/***")]
[HttpGet]
public IHttpActionResult Clear****()
{
try
{
// try clearing
}
catch(Exception e)
{
throw new ArgumentNullException(); << error occurs here
}
return this.Ok();
}
You can now put a breakpoint in your exception handler and see how the unhandled exception is caught by the global ExceptionHandler.
Quote from: https://www.exceptionnotfound.net/the-asp-net-web-api-exception-handling-pipeline-a-guided-tour/:
"The handler, like the logger, must be registered in the Web API configuration. Note that we can only have one Exception Handler per application."
config.Services.Replace(typeof(IExceptionHandler), new CustomRestErrorHandlerException ());
So add the line above to the WebApiConfig.cs file and then simply throw an exception from the controller:
[Route("api/***/***")]
[HttpGet]
public IHttpActionResult Clear****()
{
// do not use try catch here
//try
//{
// try clearing
//}
//catch(Exception e)
//{
//throw new CustomRestErrorHandlerException(); << error occurs here
//}
throw new Exception();
}
I have a basic question about basics on Web Api. FYI, I have checked before but could not found what I was looking for.
I have a piece of code as described below these lines. Just like any other Method in general terms my method called: Post, it has to return something,a JSON for example, How do I do that.
Specifically, what am I supposed to write after the word " return " in order to get the 3 fields( loginRequest.Username,loginRequest.Password,loginRequest.ContractItemId ) as Json.
Coments: Do not worry about username,password and contractID are in comments, I do get their value in my LinQ. It's just the return whta I nened now, greetings to all who would like to throw some notes about this.
[System.Web.Http.HttpPost]
public HttpResponseMessage Post(LoginModel loginRequest)
{
//loginRequest.Username = "staw_60";
//loginRequest.Password = "john31";
//loginRequest.ContractItemId = 2443;
try
{
Membership member =
(from m in db.Memberships
where
m.LoginID == loginRequest.Username
&& m.Password == loginRequest.Password
&& m.ContractItemID == loginRequest.ContractItemId
select m).SingleOrDefault();
}
catch (Exception e)
{
throw new Exception(e.Message);
}
return ???;
}
Try this:
HttpResponseMessage response = new HttpResponseMessage();
response.Content = new ObjectContent<Response>(
new Response() {
responseCode = Response.ResponseCodes.ItemNotFound
},
new JsonMediaTypeFormatter(), "application/json");
or just create another response from Request object itself.
return Request.CreateResponse<Response>(HttpStatusCode.OK,
new Response() { responseCode = Response.ResponseCodes.ItemNotFound })
You can also turn all your response types to JSON by updating the HttpConfiguration(Formatter.Remove) just remove the default xml serialization and put JSON.
You could perhaps create a LoginResponseModel class that you can use to send back information to the caller about the success/failure of the login attempt. Something like:
public class LoginResponseModel
{
public bool LoginSuccessful {get; set;}
public string ErrorMessage {get; set;}
public LoginResponseModel()
{
}
}
Then you can return this directly from the controller if you like:
[System.Web.Http.HttpPost]
public LoginResponseModel Post(LoginModel loginRequest)
{
...
return new LoginResponseModel() { LoginSuccessful = true, ErrorMessage = "" };
}
Or you can still use a HttpResponseMessage as return type, but send a LoginResponseModel as the json response:
[System.Web.Http.HttpPost]
public HttpResponseMessage Post(LoginModel loginRequest)
{
...
var resp = Request.CreateResponse<LoginResponseModel>(
HttpStatusCode.OK,
new LoginResponseModel() { LoginSuccessful = true, ErrorMessage = "" }
);
return resp;
}
I'm trying to output different formats of a type depending on the URL of the request. Up to Preview5 I did the following to get the URI in the MediaTypeFormatters OnWriteToStream-Method:
var requestUri = OperationContext.Current
.IncomingMessageHeaders
.To;
But with Preview6 the OperationContext.Current property is always null. Probably because the formatter gets executed on a different thread. So what is the correct way to get the URI in the MediaTypeFormatter? Or is there an alternative to the MediaTypeFormatter which has the request as argument?
Thank you in advance.
Regards
...
Joachim
You can use an UriFormatExtensionMessageChannel / OperationHandler as shown here.
For the sake of completeness I settled with the following solution
public class RazorHtmlHandler : HttpOperationHandler<HttpResponseMessage, HttpResponseMessage>
{
public static readonly String OUTPUT_PARAMETER_NAME = "response";
public static readonly MediaTypeWithQualityHeaderValue HTML_MEDIA_TYPE = new MediaTypeWithQualityHeaderValue("text/html");
public const String DEFAULT_TEMPLATE_NAME = "index.cshtml";
public const String DEFAULT_TEMPLATE_EXTENSION = ".cshtml";
public const String DEFAULT_RAZOR_NAME = "_RazorHtmlProcessor_Template";
public RazorHtmlHandler() : base(OUTPUT_PARAMETER_NAME)
{ }
protected override HttpResponseMessage OnHandle(HttpResponseMessage response)
{
var request = response.RequestMessage;
var accept = request.Headers.Accept;
if (!accept.Contains(HTML_MEDIA_TYPE))
return response;
var buffer = new StringBuilder();
var currentContent = response.Content as ObjectContent;
try
{
var template = LoadTemplateForResponse(request.RequestUri, currentContent);
var value = ReadValueFormObjectContent(currentContent);
buffer.Append(InvokeRazorParse(template, value));
}
catch (Exception ex)
{
throw new HttpResponseException(HttpStatusCode.InternalServerError);
}
response.Content = new StringContent(buffer.ToString(),
Encoding.UTF8,
HTML_MEDIA_TYPE.MediaType);
return response;
}
...
}
We also encountered this problem with a MediaTypeFormatter for our Web API but we solved it by simply using HttpContext.Current.Request.Url instead of going through OperationContext.Current.