I am trying to manually write my response stream and close it so that I can continue doing some stuff after the response is closed. I acheive this successfully by doing the following:
Response.StatusCode = 200
Response.ContentType = "application/json; charset=utf-8"
Response.Write(j)
Response.Flush()
Response.Close()
DOWORK()
This works perfect in most instances, however for Chrome / Flash, there is a bug in flash were it is causing this to assume it's an IO error. When analyzing the headers, the difference between manually sending a response with Return Json(results) and how I did it above is that when I return the data normally it uses a header of:
Content-Length: 44
Where as when I send it with the code above I get:
Transfer-Encoding: chunked
Is it possible to do what I want but not have the data chunked? I know this is not ASP.net specific, rather a bug in flash for chrome, but I would like to solve this.
Following my comment, I was thinking about something like:
public class CustomResult : JsonResult
{
private Action afterAction;
private object obj = null;
public CustomResult(object obj, Action afterAction) : base()
{
this.JsonRequestBehavior = System.Web.Mvc.JsonRequestBehavior.AllowGet;
this.Data = obj;
this.afterAction = afterAction;
}
public override void ExecuteResult(ControllerContext context)
{
base.ExecuteResult(context);
afterAction();
}
}
Now you could call it in controller action:
return new CustomResult(obj, () => { //custom code here, will be executed later });
Related
I have been trying to implement an event driven push to a client browser. I am using ReactiveX to produce the async task from the events but I can't even get my HttpHandlers to output their response.
I have tried with a simple HttpHandler:
public class Handler2 : IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "text/event-stream";
HttpResponse response = context.Response;
DateTime startdate = DateTime.Now;
while (startdate.AddMinutes(10) > DateTime.Now)
{
JavaScriptSerializer js = new JavaScriptSerializer();
string responseText = DateTime.Now.TimeOfDay.ToString();
response.Write(string.Format("data: {0}",js.Serialize(responseText)));
response.Flush();
System.Threading.Thread.Sleep(1000);
}
response.Close();
}
public bool IsReusable
{
get
{
return false;
}
}
}
with the following client side code:
function initialize() {
if (window.EventSource == undefined) {
document.getElementById('targetDiv').innerHTML = "Your browser doesn't support Server Side Events.";
return;
}
var source = new EventSource('Handler2.ashx');
source.onopen = function (event) {
document.getElementById('targetDiv').innerHTML += 'Connection Opened.<br>';
};
source.onerror = function (event) {
if (event.eventPhase == EventSource.CLOSED) {
document.getElementById('targetDiv').innerHTML += 'Connection Closed.<br>';
}
};
source.onmessage = function (event) {
document.getElementById('targetDiv').innerHTML += event.data + '<br>';
};
}
I have more a more complex HttpTaskAsyncHandler ready to hook up, but I can't even get this working >_<
I get the Connection Opened message, Handler2.ashx appears to remain connected (Looking at Chrome dev tools / Network).
I am, on the other hand, getting some data from a SignalR connection?
"ws://localhost:50022/ed4b66c7eb394a8789b5f6a631f4ff09/arterySignalR/connect?.."
Have I set it up wrong?
As far as I've seen on other examples, this code should be working as-is. Please could anyone help me. I just want a simple SSE control that I can trigger from server side events.
Thanks in advance
I had given this answer before, but let me elaborate:
Looking at the Network tab in Google Chrome developer tools reveals quite a lot from your http://live.meetscoresonline.com/test-sse.aspx
There are no SSE being generated at all - to see this click on the Others button under Network, this is where you would normally be able to track the SSE data stream
I use the following code in my SSE's with a simple HTTPListener and it works well without the delays you mentioned, and always shows up correctly across browsers when using this polyfill
res.AddHeader("Content-Type", "text/event-stream")
res.AddHeader("Cache-Control", "no-cache")
res.AddHeader("Access-Control-Allow-Origin", "*")
res.KeepAlive = True
I'm trying to drag and drop file upload with a progress bar.
I have a div which is listening to files being dropped on which is working perfectly.
I'm then..
//Setting up a XmlHttpRequest
xhr = new XMLHttpRequest();
//Open connection
xhr.open("post", "api/ImageUpload", true);
// Set appropriate headers
xhr.setRequestHeader("Content-Type", "multipart/form-data");
xhr.setRequestHeader("X-File-Type", uf.type);
xhr.setRequestHeader("X-File-Name", uf.name);
xhr.setRequestHeader("X-File-Size", uf.size);
This sends fine, with the stream as the body of the request to the Web API (not async).
[System.Web.Mvc.HttpPost]
public string Post()
{
Stream stream = HttpContext.Current.Request.InputStream;
String filename = HttpContext.Current.Request.Headers["X-File-Name"];
FileModel file = uploadService.UploadFile(stream, filename);
return file.Id.ToString();
}
I'm trying to chance the request to "public async Task< string> Post(){ }
If the method was using a multipart form on the page instead of XmlHttpRequest I would have used "await Request.Content.ReadAsMultipartAsync(provider)" but this doesn't seem to be populated at the time I need it.
So what is the correct was to handle and an Async call from XmlHttpRequest on a Web API in order to record progress during the request with XHR's progress event?
I have looked at a great deal of pages so far to find a solution but this is the page I have used primarily.
http://robertnyman.com/html5/fileapi-upload/fileapi-upload.html
Thanks for any help
Oliver
It looks like someone else had the same question with you and got an answer yet. please have a look at ASP.NET MVC 4 Web Api ajax file upload.
And here is an example from microsoft http://www.asp.net/web-api/overview/working-with-http/sending-html-form-data,-part-2.
I combined the two above solution together and worked for me (just adjust a little bit)
one line change in Javascritp
xhr.open("post", "api/upload", true);
Save the file using stream
public class UploadController : ApiController
{
public async Task<HttpResponseMessage> PostFormData()
{
string root = HttpContext.Current.Server.MapPath("~/App_Data");
var fileName = Path.Combine(root, Request.Headers.GetValues("X-File-Name").First());
try
{
var writer = new StreamWriter(fileName);
await Request.Content.CopyToAsync(writer.BaseStream);
writer.Close();
return Request.CreateResponse(HttpStatusCode.OK);
}
catch (System.Exception e)
{
return Request.CreateErrorResponse(HttpStatusCode.InternalServerError, e);
}
}
}
I get this error in my client (an ASP.NET MVC application) from a call to my ASP.NET Web API. I checked and the Web API is returning the data alright.
No MediaTypeFormatter is available to read an object of type
'IEnumerable`1' from content with media type 'text/plain'.
I believe that I can inherit from DataContractSerializer and implement my own serializer which can attach the Content-Type HTTP header as text/xml.
But my question is: is that necessary?
Because if it was, it would mean that the default DataContractSerializer does not set this essential header. I was wondering if Microsoft could leave such an important thing out. Is there another way out?
Here's the relevant client side code:
public ActionResult Index()
{
HttpClient client = new HttpClient();
var response = client.GetAsync("http://localhost:55333/api/bookreview/index").Result;
if (response.IsSuccessStatusCode)
{
IEnumerable<BookReview> reviews = response.Content.ReadAsAsync<IEnumerable<BookReview>>().Result;
return View(reviews);
}
else
{
ModelState.AddModelError("", string.Format("Reason: {0}", response.ReasonPhrase));
return View();
}
}
And here's the server side (Web API) code:
public class BookReviewController : ApiController
{
[HttpGet]
public IEnumerable<BookReview> Index()
{
try
{
using (var context = new BookReviewEntities())
{
context.ContextOptions.ProxyCreationEnabled = false;
return context.BookReviews.Include("Book.Author");
}
}
catch (Exception ex)
{
var responseMessage = new HttpResponseMessage
{
Content = new StringContent("Couldn't retrieve the list of book reviews."),
ReasonPhrase = ex.Message.Replace('\n', ' ')
};
throw new HttpResponseException(responseMessage);
}
}
}
I believe (because I don't have time to test it now) that you need to explicitly set the Status Code on the responseMessage you are passing to HttpResponseException. Normally, HttpResponseException will set the status code for you, but because you are providing a responsemessage explicitly, it will use the status code from that. By default, `HttpResponseMessage has a status code of 200.
So what is happening is you are getting an error on the server, but still returning a 200. Which is why your client is trying to deserialize the text/plain body produced by StringContent, as if it were an IEnumerable.
You need to set
responseMessage.StatusCode = HttpStatusCode.InternalServerError
in your exception handler on the server.
How about just using ReadAsStringAsync if your WebAPI is expecting to return content in plain text?
response.Content.ReadAsStringAsync().Result;
I'm using Web API to stream large files to clients, but I'd like to log if the download was successful or not. That is, if the server sent the entire content of the file.
Is there some way to get a a callback or event when the HttpResponseMessage completes sending data?
Perhaps something like this:
var stream = GetMyStream();
var response = new HttpResponseMessage(HttpStatusCode.OK);
response.Content = new StreamContent(stream);
response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
// This doesn't exist, but it illustrates what I'm trying to do.
response.OnComplete(context =>
{
if (context.Success)
Log.Info("File downloaded successfully.");
else
Log.Warn("File download was terminated by client.");
});
EDIT: I've now tested this using a real connection (via fiddler).
I inherited StreamContent and added my own OnComplete action which checks for an exception:
public class StreamContentWithCompletion : StreamContent
{
public StreamContentWithCompletion(Stream stream) : base (stream) { }
public StreamContentWithCompletion(Stream stream, Action<Exception> onComplete) : base(stream)
{
this.OnComplete = onComplete;
}
public Action<Exception> OnComplete { get; set; }
protected override Task SerializeToStreamAsync(Stream stream, TransportContext context)
{
var t = base.SerializeToStreamAsync(stream, context);
t.ContinueWith(x =>
{
if (this.OnComplete != null)
{
// The task will be in a faulted state if something went wrong.
// I observed the following exception when I aborted the fiddler session:
// 'System.Web.HttpException (0x800704CD): The remote host closed the connection.'
if (x.IsFaulted)
this.OnComplete(x.Exception.GetBaseException());
else
this.OnComplete(null);
}
}, TaskContinuationOptions.ExecuteSynchronously);
return t;
}
}
Then I use it like so:
var stream = GetMyStream();
var response = new HttpResponseMessage(HttpStatusCode.OK);
response.Content = new StreamContentWithCompletion(stream, ex =>
{
if (ex == null)
Log.Info("File downloaded successfully.");
else
Log.Warn("File download was terminated by client.");
});
response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
return response;
I am not sure if there is direct signaling that all is ok, but you can use a trick to find out that the connection is exist just before you end it up, and right after you fully send the file.
For example the Response.IsClientConnected is return true if the client is still connected, so you can check something like:
// send the file, make a flush
Response.Flush();
// and now the file is fully sended check if the client is still connected
if(Response.IsClientConnected)
{
// log that all looks ok until the last byte.
}
else
{
// the client is not connected, so maybe have lost some data
}
// and now close the connection.
Response.End();
if the server sent the entire content of the file
Actually there is nothing to do :)
This might sound very simplistic but you will know if an exception is raised - if you care about server delivering and not client cancelling halfway. IsClientConnected is based on ASP.NET HttpResponse not the WebApi.
My goal is to authenticate Web API requests using a AuthorizationFilter or DelegatingHandler. I want to look for the client id and authentication token in a few places, including the request body. At first it seemed like this would be easy, I could do something like this
var task = _message.Content.ReadAsAsync<Credentials>();
task.Wait();
if (task.Result != null)
{
// check if credentials are valid
}
The problem is that the HttpContent can only be read once. If I do this in a Handler or a Filter then the content isn't available for me in my action method. I found a few answers here on StackOverflow, like this one: Read HttpContent in WebApi controller that explain that it is intentionally this way, but they don't say WHY. This seems like a pretty severe limitation that blocks me from using any of the cool Web API content parsing code in Filters or Handlers.
Is it a technical limitation? Is it trying to keep me from doing a VERY BAD THING(tm) that I'm not seeing?
POSTMORTEM:
I took a look at the source like Filip suggested. ReadAsStreamAsync returns the internal stream and there's nothing stopping you from calling Seek if the stream supports it. In my tests if I called ReadAsAsync then did this:
message.Content.ReadAsStreamAsync().ContinueWith(t => t.Result.Seek(0, SeekOrigin.Begin)).Wait();
The automatic model binding process would work fine when it hit my action method. I didn't use this though, I opted for something more direct:
var buffer = new MemoryStream(_message.Content.ReadAsByteArrayAsync().WaitFor());
var formatters = _message.GetConfiguration().Formatters;
var reader = formatters.FindReader(typeof(Credentials), _message.Content.Headers.ContentType);
var credentials = reader.ReadFromStreamAsync(typeof(Credentials), buffer, _message.Content, null).WaitFor() as Credentials;
With an extension method (I'm in .NET 4.0 with no await keyword)
public static class TaskExtensions
{
public static T WaitFor<T>(this Task<T> task)
{
task.Wait();
if (task.IsCanceled) { throw new ApplicationException(); }
if (task.IsFaulted) { throw task.Exception; }
return task.Result;
}
}
One last catch, HttpContent has a hard-coded max buffer size:
internal const int DefaultMaxBufferSize = 65536;
So if your content is going to be bigger than that you'll need to manually call LoadIntoBufferAsync with a larger size before you try to call ReadAsByteArrayAsync.
The answer you pointed to is not entirely accurate.
You can always read as string (ReadAsStringAsync)or as byte[] (ReadAsByteArrayAsync) as they buffer the request internally.
For example the dummy handler below:
public class MyHandler : DelegatingHandler
{
protected override async System.Threading.Tasks.Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
{
var body = await request.Content.ReadAsStringAsync();
//deserialize from string i.e. using JSON.NET
return base.SendAsync(request, cancellationToken);
}
}
Same applies to byte[]:
public class MessageHandler : DelegatingHandler
{
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
var requestMessage = await request.Content.ReadAsByteArrayAsync();
//do something with requestMessage - but you will have to deserialize from byte[]
return base.SendAsync(request, cancellationToken);
}
}
Each will not cause the posted content to be null when it reaches the controller.
I'd put the clientId and the authentication key in the header rather than content.
In which way, you can read them as many times as you like!