I am trying to create a custom JSONMediaTypeFormatter in which posts some json parameters to a webapi call. I need to encrypt the returned data from the webapi, hence writing a custom mediatypeformatter.
In my webapiconfig I clear all formatters and only add the custom formatter.
config.Formatters.Clear();
config.Formatters.Add(new CipherMediaFormatter());
In my custom media type formatter I add in the relevant headers and types but i still cant call my web api. It gives me an error
No MediaTypeFormatter is available to read an object of type 'Param' from content with media type 'application/json
The code for the mediatypeformatter
public class CipherMediaFormatter : JsonMediaTypeFormatter
{
private static Type _supportedType = typeof(object);
public CipherMediaFormatter()
{
this.SupportedMediaTypes.Add(new MediaTypeHeaderValue("application/octet-stream"));
this.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html"));
this.SupportedMediaTypes.Add(new MediaTypeHeaderValue("application/json"));
}
public override void SetDefaultContentHeaders(Type type, HttpContentHeaders headers, MediaTypeHeaderValue mediaType)
{
base.SetDefaultContentHeaders(type, headers, mediaType);
headers.ContentType = new MediaTypeHeaderValue("application/json");
}
public override bool CanReadType(Type type)
{
return true;
}
public override bool CanWriteType(Type type)
{
return true;
}
public override Task<object> ReadFromStreamAsync(Type type, Stream readStream, HttpContent content, IFormatterLogger formatterLogger)
{
var taskSource = new TaskCompletionSource<object>();
try
{
var ms = new MemoryStream();
readStream.CopyTo(ms);
taskSource.SetResult(ms.ToArray());
}
catch (Exception e)
{
taskSource.SetException(e);
}
return taskSource.Task;
}
public override Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content, TransportContext transportContext)
{
var taskSource = new TaskCompletionSource<object>();
try
{
if (value != null)
{
var jsonData = JsonConvert.SerializeObject(value);
ICryptographicService cgService = new CryptographicService();
string apiKey = string.Empty;
string pattern = #"api\/(.*)?\/(\d+)?";
var match = Regex.Match(HttpContext.Current.Request.RawUrl, pattern);
....
}
}
catch (Exception e)
{
taskSource.SetException(e);
}
return taskSource.Task;
}
}
The problem was ReadFromStreamAsync causing the mediatypeformatter to error.
Related
I have a controller action Export which accepts a List of models like below. This is sending back and manipulated dataset back from the view where the user could interact with it. So we have been able to send the data down with much more information.
[HttpPost]
public JsonResult Export(List<MappingExportModel> sources){}
This works fine in all cases but there is one where we have a bigger than normal dataset. This is causing an issue with the export. So far I have tried just passing the values as an object or string but I am unable to convert them into any usable instance after the data is into the controller.
Is it possible to preemptively increase this maxjsonlength value somewhere. The value from the web.config is being ignored from what I have come across so far.
The error I receive is
"Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property"
I need to be able to accept this directly from the ajax request into the controller action. Spinning up a version of JsonResult and then setting the max value will not work because the error is thrown the the data is trying to be deserialized into the object var presented above. We get the value in the original GET request and do set the value before the view is loaded. Now we are taking the data from this view and sending it back plus all the manipulations the users have created.
User posts data to server, the controller action is hit with the data. The error is encountered and spit back out to the browser which handles the error.
You can use custom json length. add the following file in your project and edit your global.asax.cs
Global.asax
public class MvcApplication : System.Web.HttpApplication
{
protected void Application_Start()
{
AreaRegistration.RegisterAllAreas();
WebApiConfig.Register(GlobalConfiguration.Configuration);
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
RouteConfig.RegisterRoutes(RouteTable.Routes);
BundleConfig.RegisterBundles(BundleTable.Bundles);
///// **********
JsonValueProviderFactory jsonValueProviderFactory = null;
foreach (var factory in ValueProviderFactories.Factories)
{
if (factory is JsonValueProviderFactory)
{
jsonValueProviderFactory = factory as JsonValueProviderFactory;
}
}
//remove the default JsonVAlueProviderFactory
if (jsonValueProviderFactory != null) ValueProviderFactories.Factories.Remove(jsonValueProviderFactory);
//add the custom one
ValueProviderFactories.Factories.Add(new CustomJsonValueProviderFactory());
/////*************
}
}
///******** for json length
public sealed class CustomJsonValueProviderFactory : ValueProviderFactory
{
private static void AddToBackingStore(Dictionary<string, object> backingStore, string prefix, object value)
{
IDictionary<string, object> d = value as IDictionary<string, object>;
if (d != null)
{
foreach (KeyValuePair<string, object> entry in d)
{
AddToBackingStore(backingStore, MakePropertyKey(prefix, entry.Key), entry.Value);
}
return;
}
IList l = value as IList;
if (l != null)
{
for (int i = 0; i < l.Count; i++)
{
AddToBackingStore(backingStore, MakeArrayKey(prefix, i), l[i]);
}
return;
}
// primitive
backingStore[prefix] = value;
}
private static object GetDeserializedObject(ControllerContext controllerContext)
{
if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
{
// not JSON request
return null;
}
StreamReader reader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
string bodyText = reader.ReadToEnd();
if (String.IsNullOrEmpty(bodyText))
{
// no JSON data
return null;
}
JavaScriptSerializer serializer = new JavaScriptSerializer();
serializer.MaxJsonLength = int.MaxValue; //increase MaxJsonLength. This could be read in from the web.config if you prefer
object jsonData = serializer.DeserializeObject(bodyText);
return jsonData;
}
public override IValueProvider GetValueProvider(ControllerContext controllerContext)
{
if (controllerContext == null)
{
throw new ArgumentNullException("controllerContext");
}
object jsonData = GetDeserializedObject(controllerContext);
if (jsonData == null)
{
return null;
}
Dictionary<string, object> backingStore = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
AddToBackingStore(backingStore, String.Empty, jsonData);
return new DictionaryValueProvider<object>(backingStore, CultureInfo.CurrentCulture);
}
private static string MakeArrayKey(string prefix, int index)
{
return prefix + "[" + index.ToString(CultureInfo.InvariantCulture) + "]";
}
private static string MakePropertyKey(string prefix, string propertyName)
{
return (String.IsNullOrEmpty(prefix)) ? propertyName : prefix + "." + propertyName;
}
}
JsonValueProviderFactory.cs
public sealed class JsonValueProviderFactory : ValueProviderFactory
{
private static void AddToBackingStore(Dictionary<string, object> backingStore, string prefix, object value)
{
IDictionary<string, object> d = value as IDictionary<string, object>;
if (d != null)
{
foreach (KeyValuePair<string, object> entry in d)
{
AddToBackingStore(backingStore, MakePropertyKey(prefix, entry.Key), entry.Value);
}
return;
}
IList l = value as IList;
if (l != null)
{
for (int i = 0; i < l.Count; i++)
{
AddToBackingStore(backingStore, MakeArrayKey(prefix, i), l[i]);
}
return;
}
// primitive
backingStore[prefix] = value;
}
private static object GetDeserializedObject(ControllerContext controllerContext)
{
if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
{
// not JSON request
return null;
}
StreamReader reader = new StreamReader(controllerContext.HttpContext.Request.InputStream);
string bodyText = reader.ReadToEnd();
if (String.IsNullOrEmpty(bodyText))
{
// no JSON data
return null;
}
JavaScriptSerializer serializer = new JavaScriptSerializer();
serializer.MaxJsonLength = int.MaxValue; //increase MaxJsonLength. This could be read in from the web.config if you prefer
object jsonData = serializer.DeserializeObject(bodyText);
return jsonData;
}
public override IValueProvider GetValueProvider(ControllerContext controllerContext)
{
if (controllerContext == null)
{
throw new ArgumentNullException("controllerContext");
}
object jsonData = GetDeserializedObject(controllerContext);
if (jsonData == null)
{
return null;
}
Dictionary<string, object> backingStore = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
AddToBackingStore(backingStore, String.Empty, jsonData);
return new DictionaryValueProvider<object>(backingStore, CultureInfo.CurrentCulture);
}
private static string MakeArrayKey(string prefix, int index)
{
return prefix + "[" + index.ToString(CultureInfo.InvariantCulture) + "]";
}
private static string MakePropertyKey(string prefix, string propertyName)
{
return (String.IsNullOrEmpty(prefix)) ? propertyName : prefix + "." + propertyName;
}
}
by this you can pass lengthy json through ajax to controller and if you want to retrieve a lengthy string back to ajax result from controller then add below code in your controller also
//add this for getting large json string
protected override JsonResult Json(object data, string contentType, System.Text.Encoding contentEncoding, JsonRequestBehavior behavior)
{
return new JsonResult()
{
Data = data,
ContentType = contentType,
ContentEncoding = contentEncoding,
JsonRequestBehavior = behavior,
MaxJsonLength = Int32.MaxValue
};
}
I am calling a post action on a webapi by passing in a serialised JSON DTO.
I also have a custom media type formatter to encrypt the resulting data. However in the WriteToStreamAsync method, how can i get the posted parameters?
The custom media type formatter class
public class JsonFormatter : JsonMediaTypeFormatter
{
public override Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content, TransportContext transportContext)
{
var taskSource = new TaskCompletionSource<object>();
try
{
if (value != null)
{
//How to get posted parameters?
}
}
catch (Exception e)
{
taskSource.SetException(e);
}
return taskSource.Task;
}
}
}
I managed to get it via the HttpContext.Current.Request.InputStream
Using HttpContext.Current generally should not work in this scenario since it won't always be available for async calls.
Instead do something like this:
public class JsonFormatter : JsonMediaTypeFormatter
{
private readonly HttpRequestMessage request;
public JsonFormatter() { }
public JsonFormatter(HttpRequestMessage request)
{
this.request = request;
}
public override MediaTypeFormatter GetPerRequestFormatterInstance(Type type, HttpRequestMessage request, MediaTypeHeaderValue mediaType)
{
return new JsonFormatter(request);
}
public override Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content, TransportContext transportContext)
{
// logic referencing this.request
}
}
How to force WCF Rest client to use Json deserializer regardless of content-type?
I am invoking a REST based web service through WCF.
The service returns JSON body, but has content-type "Application/xml". The WCF framework is now giving me the XmlException.
public class MessageFormatter : IClientMessageFormatter
{
private readonly IClientMessageFormatter _formatter;
public MessageFormatter(IClientMessageFormatter formatter)
{
_formatter = formatter;
}
public object DeserializeReply(System.ServiceModel.Channels.Message message, object[] parameters)
{
return _formatter.DeserializeReply(message, parameters);
}
}
that _formatter.DeserializeReply is throwing XmlException. I can't find any example anywhere to force json deserialization on reply.
Edit - The "message" object when moused over is throwing "{... Error reading body: System.Xml.XmlException: The data at the root level is invalid. Line 1, position 1. ...}"
That same object in another one of my project that communicate with a different REST service (Picasa web services) has a what seems like a xml serialised version of JSON object?? So the problem seems further up the stream. I need to find where this object is originating from. I'll go play around with MessageEncoder class.
Edit - (Adding more info)
public class MyBinding : WebHttpBinding
{
public MyBinding(WebHttpSecurityMode mode)
: base(mode)
{
}
public override BindingElementCollection CreateBindingElements()
{
var result = base.CreateBindingElements();
var replacements = result.OfType<MessageEncodingBindingElement>().ToList();
foreach (var messageEncodingBindingElement in replacements)
{
var index = result.IndexOf(messageEncodingBindingElement);
result.Remove(messageEncodingBindingElement);
result.Insert(index, new MyMessageEncodingBindingElement(messageEncodingBindingElement));
}
return result;
}
}
public class MyMessageEncodingBindingElement : MessageEncodingBindingElement
{
private readonly MessageEncodingBindingElement _element;
public MyMessageEncodingBindingElement(MessageEncodingBindingElement element)
{
_element = element;
}
public override BindingElement Clone()
{
var result = _element.Clone();
if (result is MessageEncodingBindingElement)
return new MyMessageEncodingBindingElement(result as MessageEncodingBindingElement);
return result;
}
public override MessageEncoderFactory CreateMessageEncoderFactory()
{
return new MyMessageEncoderFactory(_element.CreateMessageEncoderFactory());
}
}
The method CreateMessageEncoderFactory() is never called even when the constructor and Clone method are hit when breakpoints are set. Any help? I'm trying to set a custom MessageEncoder and MessageEncoderFactory class to modify the instantiation process of the Message object.
You can use a WebContentTypeMapper for that. That's a property of the WebHttpBinding, and you can customize how the deserialization will be done by the encoder from that binding, including forcing it to always use the JSON deserializer, regardless of the incoming message's Content-Type. The code below shows how this can be done.
public class StackOverflow_13225272
{
[DataContract]
public class Person
{
[DataMember]
public string Name { get; set; }
[DataMember]
public int Age { get; set; }
public override string ToString()
{
return string.Format("Person[Name={0},Age={1}]", Name, Age);
}
}
[ServiceContract]
public interface ITest
{
[WebGet(ResponseFormat = WebMessageFormat.Json)]
Person GetPerson(string responseContentType);
}
public class Service : ITest
{
public Person GetPerson(string responseContentType)
{
WebOperationContext.Current.OutgoingResponse.ContentType = responseContentType;
return new Person { Name = "John Doe", Age = 29 };
}
}
class AllJsonContentTypeMapper : WebContentTypeMapper
{
public override WebContentFormat GetMessageFormatForContentType(string contentType)
{
return WebContentFormat.Json;
}
}
public static void Test()
{
string baseAddress = "http://" + Environment.MachineName + ":8000/Service";
WebServiceHost host = new WebServiceHost(typeof(Service), new Uri(baseAddress));
host.Open();
Console.WriteLine("Host opened");
#if USE_NETFX4
// This works on .NET 4.0 and beyond
WebHttpBinding binding = new WebHttpBinding();
binding.ContentTypeMapper = new AllJsonContentTypeMapper();
#else
// This works on .NET 3.5
CustomBinding binding = new CustomBinding(new WebHttpBinding());
binding.Elements.Find<WebMessageEncodingBindingElement>().ContentTypeMapper = new AllJsonContentTypeMapper();
ChannelFactory<ITest> factory = new ChannelFactory<ITest>(binding, new EndpointAddress(baseAddress));
#endif
ChannelFactory<ITest> factory = new ChannelFactory<ITest>(binding, new EndpointAddress(baseAddress));
factory.Endpoint.Behaviors.Add(new WebHttpBehavior());
ITest proxy = factory.CreateChannel();
Console.WriteLine("With JSON: {0}", proxy.GetPerson("application/json"));
Console.WriteLine("With XML: {0}", proxy.GetPerson("application/xml"));
Console.Write("Press ENTER to close the host");
Console.ReadLine();
host.Close();
}
}
This might work.
public class ForceJsonClientMessageFormatter : IClientMessageFormatter
{
private readonly DataContractJsonSerializer _jsonSerializer;
public ForceJsonClientMessageFormatter(Type responseType)
{
_jsonSerializer = new DataContractJsonSerializer(responseType);
}
public Message SerializeRequest(MessageVersion messageVersion, object[] parameters)
{
throw new NotImplementedException("This client message formatter is for replies only!");
}
public object DeserializeReply(Message message, object[] parameters)
{
string messageBody = message.GetBody<string>();
using (MemoryStream messageStream = new MemoryStream(Encoding.UTF8.GetBytes(messageBody)))
{
messageStream.Seek(0, SeekOrigin.Begin);
object deserializedObject = _jsonSerializer.ReadObject(messageStream);
return deserializedObject;
}
}
}
public class ForceJsonWebHttpBehavior : WebHttpBehavior
{
protected override IClientMessageFormatter GetReplyClientFormatter(OperationDescription operationDescription, ServiceEndpoint endpoint)
{
return new ForceJsonClientMessageFormatter(operationDescription.Messages[1].Body.ReturnValue.Type);
}
}
I haven't tried it, but I think this will work. You can create a custom IClientMessageFormatter which overwrites the message format to Json, wrap that in a behavior, and then apply that behavior to your client endpoint configuration.
public class ForceJsonClientMessageFormatterDecorator : IClientMessageFormatter
{
private readonly IClientMessageFormatter _decoratedFormatter;
public ForceJsonClientMessageFormatterDecorator(IClientMessageFormatter decoratedFormatter)
{
_decoratedFormatter = decoratedFormatter;
}
public object DeserializeReply(Message message, object[] parameters)
{
message.Properties[WebBodyFormatMessageProperty.Name] = new WebBodyFormatMessageProperty(WebContentFormat.Json);
return _decoratedFormatter.DeserializeReply(message, parameters);
}
public Message SerializeRequest(MessageVersion messageVersion, object[] parameters)
{
return _decoratedFormatter.SerializeRequest(messageVersion, parameters);
}
}
public class ForceJsonWebHttpBehavior : WebHttpBehavior
{
protected override IClientMessageFormatter GetReplyClientFormatter(OperationDescription operationDescription, ServiceEndpoint endpoint)
{
IClientMessageFormatter decoratedFormatter = base.GetReplyClientFormatter(operationDescription, endpoint);
return new ForceJsonClientMessageFormatterDecorator(decoratedFormatter);
}
}
I have a form on a webpage that I submit using the jquery form plugin. This form includes a file upload option. The MVC3 action that I post to returns JSON. Since the plugin falls back to using an iframe on older browsers you need to wrap your JSON with a
<textarea>JSON data...</textarea>
I tried changing the return type of the action to string and just appending the text area tags the the JSON object.ToString() but no go. How can I wrap my JSON result in a textarea when !Request.IsAjaxRequest()
Here is an example of me just trying to return the JSON as a string (which doesn't work)
[HttpPost]
public string CreateEntry(EntryCreateViewModel model)
{
if (!ModelState.IsValid)
{
return WrapInTextArea(!Request.IsAjaxRequest(), Json(new object[] { false, 0, this.RenderPartialViewToString("_EntryCreateFormPartial", model) }).ToString());
}
This works in modern browsers but I suspect (based on the docs) will fail in older browsers that use an iframe
[HttpPost]
public ActionResult CreateEntry(EntryCreateViewModel model)
{
if (!ModelState.IsValid)
{
return Json(new object[] {false, 0, this.RenderPartialViewToString("_EntryCreateFormPartial", model)});
}
To solve this I inherited from JsonResult and added the textarea there
using System;
using System.Web.Mvc;
using System.Web.Script.Serialization;
namespace TinyHouseMap.Web.Infrastructure.Results
{
public class JsonInIframeResult : JsonResult
{
public bool EncloseInTextArea
{
get;
set;
}
public override void ExecuteResult(ControllerContext context)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
if ((JsonRequestBehavior == JsonRequestBehavior.DenyGet)
&& string.Equals(context.HttpContext.Request.HttpMethod, "GET", StringComparison.OrdinalIgnoreCase))
{
throw new InvalidOperationException("JsonRequest GetNotAllowed");
}
var response = context.HttpContext.Response;
response.ContentType = !string.IsNullOrEmpty(ContentType) ? ContentType : "application/json";
if (ContentEncoding != null)
{
response.ContentEncoding = ContentEncoding;
}
if (Data != null)
{
var serializer = new JavaScriptSerializer();
string results;
if (EncloseInTextArea)
{
results = "<textarea>" + serializer.Serialize(Data) + "</textarea>";
}
else
{
results = serializer.Serialize(Data);
}
response.Write(results);
}
}
}
}
And then created a helper in my controller base class
protected JsonInIframeResult JsonInIframe(object data, string contentType, bool encloseInTextArea)
{
var result = new JsonInIframeResult {Data = data, ContentType = contentType, EncloseInTextArea = encloseInTextArea};
return result;
}
I am looking to return some JSON across domains and I understand that the way to do this is through JSONP rather than pure JSON.
I am using ASP.net MVC so I was thinking about just extending the JsonResult type and then extending the Controller so that it also implemented a Jsonp method.
Is this the best way to go about it or is there a built-in ActionResult that might be better?
Solution: I went ahead and did that. Just for reference sake I added a new result:
public class JsonpResult : System.Web.Mvc.JsonResult
{
public override void ExecuteResult(ControllerContext context)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
HttpResponseBase response = context.HttpContext.Response;
if (!String.IsNullOrEmpty(ContentType))
{
response.ContentType = ContentType;
}
else
{
response.ContentType = "application/javascript";
}
if (ContentEncoding != null)
{
response.ContentEncoding = ContentEncoding;
}
if (Data != null)
{
// The JavaScriptSerializer type was marked as obsolete prior to .NET Framework 3.5 SP1
#pragma warning disable 0618
HttpRequestBase request = context.HttpContext.Request;
JavaScriptSerializer serializer = new JavaScriptSerializer();
response.Write(request.Params["jsoncallback"] + "(" + serializer.Serialize(Data) + ")");
#pragma warning restore 0618
}
}
}
and also a couple of methods to a superclass of all my controllers:
protected internal JsonpResult Jsonp(object data)
{
return Jsonp(data, null /* contentType */);
}
protected internal JsonpResult Jsonp(object data, string contentType)
{
return Jsonp(data, contentType, null);
}
protected internal virtual JsonpResult Jsonp(object data, string contentType, Encoding contentEncoding)
{
return new JsonpResult
{
Data = data,
ContentType = contentType,
ContentEncoding = contentEncoding
};
}
Works like a charm.
Here is a simple solution, if you don't want to define an action filter
Client side code using jQuery:
$.ajax("http://www.myserver.com/Home/JsonpCall", { dataType: "jsonp" }).done(function (result) {});
MVC controller action. Returns content result with JavaScript code executing callback function provided with query string. Also sets JavaScript MIME type for response.
public ContentResult JsonpCall(string callback)
{
return Content(String.Format("{0}({1});",
callback,
new JavaScriptSerializer().Serialize(new { a = 1 })),
"application/javascript");
}
Rather than subclassing my controllers with Jsonp() methods, I went the extension method route as it feels a touch cleaner to me. The nice thing about the JsonpResult is that you can test it exactly the same way you would a JsonResult.
I did:
public static class JsonResultExtensions
{
public static JsonpResult ToJsonp(this JsonResult json)
{
return new JsonpResult { ContentEncoding = json.ContentEncoding, ContentType = json.ContentType, Data = json.Data, JsonRequestBehavior = json.JsonRequestBehavior};
}
}
This way you don't have to worry about creating all the different Jsonp() overloads, just convert your JsonResult to a Jsonp one.
Ranju's blog post (aka "This blog post I found") is excellent, and reading it will allow you to further the solution below so that your controller can handle same-domain JSON and cross-domain JSONP requests elegantly in the same controller action without additional code [in the action].
Regardless, for the "give me the code" types, here it is, in case the blog disappears again.
In your controller (this snippet is new/non-blog code):
[AllowCrossSiteJson]
public ActionResult JsonpTime(string callback)
{
string msg = DateTime.UtcNow.ToString("o");
return new JsonpResult
{
Data = (new
{
time = msg
})
};
}
JsonpResult found on
this excellent blog post:
/// <summary>
/// Renders result as JSON and also wraps the JSON in a call
/// to the callback function specified in "JsonpResult.Callback".
/// http://blogorama.nerdworks.in/entry-EnablingJSONPcallsonASPNETMVC.aspx
/// </summary>
public class JsonpResult : JsonResult
{
/// <summary>
/// Gets or sets the javascript callback function that is
/// to be invoked in the resulting script output.
/// </summary>
/// <value>The callback function name.</value>
public string Callback { get; set; }
/// <summary>
/// Enables processing of the result of an action method by a
/// custom type that inherits from <see cref="T:System.Web.Mvc.ActionResult"/>.
/// </summary>
/// <param name="context">The context within which the
/// result is executed.</param>
public override void ExecuteResult(ControllerContext context)
{
if (context == null)
throw new ArgumentNullException("context");
HttpResponseBase response = context.HttpContext.Response;
if (!String.IsNullOrEmpty(ContentType))
response.ContentType = ContentType;
else
response.ContentType = "application/javascript";
if (ContentEncoding != null)
response.ContentEncoding = ContentEncoding;
if (Callback == null || Callback.Length == 0)
Callback = context.HttpContext.Request.QueryString["callback"];
if (Data != null)
{
// The JavaScriptSerializer type was marked as obsolete
// prior to .NET Framework 3.5 SP1
#pragma warning disable 0618
JavaScriptSerializer serializer = new JavaScriptSerializer();
string ser = serializer.Serialize(Data);
response.Write(Callback + "(" + ser + ");");
#pragma warning restore 0618
}
}
}
Note: Following up on the comments to the OP by #Ranju and others, I figured it was worth posting the "bare minimum" functional code from Ranju's blog post as a community wiki. Though it's safe to say that Ranju added the above and other code on his blog to be used freely, I'm not going to copy his words here.
For ASP.NET Core ,NOT ASP.NET MVC
This is a tailored version for ASP.NET CORE of the solution which exists in the answer
public class JsonpResult : JsonResult
{
public JsonpResult(object value) : base(value)
{
}
public override async Task ExecuteResultAsync(ActionContext context)
{
if (context == null)
throw new ArgumentNullException(nameof(context));
HttpResponse response = context.HttpContext.Response;
if (!String.IsNullOrEmpty(ContentType))
response.ContentType = ContentType;
else
response.ContentType = "application/javascript";
if (Value != null)
{
HttpRequest request = context.HttpContext.Request;
string serializedJson = JsonConvert.SerializeObject(Value);
string result = $"{request.Query["callback"]}({serializedJson})";
await response.WriteAsync(result);
}
}
}
The referenced articles by stimms and ranju v were both very useful and made the situation clear.
However, I was left scratching my head about using extensions, sub-classing in context of the MVC code I had found online.
There was two key points that caught me out:
The code I had derived from ActionResult, but in ExecuteResult there was some code to return either XML or JSON.
I had then created a Generics based ActionResult, to ensure the same ExecuteResults was used independant of the type of data I returned.
So, combining the two - I did not need further extensions or sub-classing to add the mechanism to return JSONP, simply change my existing ExecuteResults.
What had confused me is that really I was looking for a way to derive or extend JsonResult, without re-coding the ExecuteResult. As JSONP is effectively a JSON string with prefix & suffix it seemed a waste. However the underling ExecuteResult uses respone.write - so the safest way of changing is to re-code ExecuteResults as handily provided by various postings!
I can post some code if that would be useful, but there is quite a lot of code in this thread already.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Script.Serialization;
namespace Template.Web.Helpers
{
public class JsonpResult : JsonResult
{
public JsonpResult(string callbackName)
{
CallbackName = callbackName;
}
public JsonpResult()
: this("jsoncallback")
{
}
public string CallbackName { get; set; }
public override void ExecuteResult(ControllerContext context)
{
if (context == null)
{
throw new ArgumentNullException("context");
}
var request = context.HttpContext.Request;
var response = context.HttpContext.Response;
string jsoncallback = ((context.RouteData.Values[CallbackName] as string) ?? request[CallbackName]) ?? CallbackName;
if (!string.IsNullOrEmpty(jsoncallback))
{
if (string.IsNullOrEmpty(base.ContentType))
{
base.ContentType = "application/x-javascript";
}
response.Write(string.Format("{0}(", jsoncallback));
}
base.ExecuteResult(context);
if (!string.IsNullOrEmpty(jsoncallback))
{
response.Write(")");
}
}
}
public static class ControllerExtensions
{
public static JsonpResult Jsonp(this Controller controller, object data, string callbackName = "callback")
{
return new JsonpResult(callbackName)
{
Data = data,
JsonRequestBehavior = JsonRequestBehavior.AllowGet
};
}
public static T DeserializeObject<T>(this Controller controller, string key) where T : class
{
var value = controller.HttpContext.Request.QueryString.Get(key);
if (string.IsNullOrEmpty(value))
{
return null;
}
JavaScriptSerializer javaScriptSerializer = new JavaScriptSerializer();
return javaScriptSerializer.Deserialize<T>(value);
}
}
}
//Example of using the Jsonp function::
// 1-
public JsonResult Read()
{
IEnumerable<User> result = context.All();
return this.Jsonp(result);
}
//2-
public JsonResult Update()
{
var models = this.DeserializeObject<IEnumerable<User>>("models");
if (models != null)
{
Update(models); //Update properties & save change in database
}
return this.Jsonp(models);
}
the solution above is a good way of working but it should be extendend with a new type of result instead of having a method that returns a JsonResult you should write methods that return your own result types
public JsonPResult testMethod() {
// use the other guys code to write a method that returns something
}
public class JsonPResult : JsonResult
{
public FileUploadJsonResult(JsonResult data) {
this.Data = data;
}
public override void ExecuteResult(ControllerContext context)
{
this.ContentType = "text/html";
context.HttpContext.Response.Write("<textarea>");
base.ExecuteResult(context);
context.HttpContext.Response.Write("</textarea>");
}
}