I have a strange problem, that appears not always, but sometimes with the same request.
On my website (localhost) I have an ExtJS store with autoloading, and after page load (pushing F5 button) it reads JSON from some handler (*.ashx) from server. Handler gets data from DB and serializes it it JSON. It works 4 times of 5 pressing F5. 5th time json-reader shows success=false and 0 length data.
If I use time delay in handler, such as:
System.Threading.Thread.Sleep(1000);
It works 49 times of 50. But it is weird to set a latency in my response, when I try to make website faster.
Please help or ask me if there is not enough info about a problem!
Here is sample of my js:
storePrefixes.on({
'beforeload': function () {
//...
},
'load': {
fn: function() {
if (storePrefixes.data.items.length > 0)
// ... working with response
else
// here is a problem
},
single: true
}
});
And there is server code:
<%# WebHandler Language="C#" Class="GetPrefixesInRD" %>
using System;
using System.Web;
using BCR.BLL;
public class GetPrefixesInRD : IHttpHandler, System.Web.SessionState.IReadOnlySessionState
{
private readonly PrefixNewBLL prefixeBLL = new PrefixNewBLL();
private readonly Newtonsoft.Json.JsonSerializer serializer = new Newtonsoft.Json.JsonSerializer();
public void ProcessRequest(HttpContext context)
{
var prefixes = prefixeBLL.GetPrefixesByExistPrefixInAccountingDocs(null, 1, false);
prefixes.Sort((x, y) => String.CompareOrdinal(x.Prefix, y.Prefix));
context.Response.ContentType = "application/json";
context.Response.Clear();
context.Response.BufferOutput = true;
serializer.Serialize(context.Response.Output, new { root = prefixes, total = prefixes.Count });
context.Response.Flush();
context.Response.End();
}
public bool IsReusable { get { return false; } }
}
When debugging, I would check this.isLoading() to see if it is still trying to load on the odd man out. It might be better to move everything to the datachanged event. If you need to analyze the store, use console.dir(Ext.apply({}, this)); to get a snapshot at runtime.
Related
So i'm testing with Blazor and gRPC and my dificulty at the moment is on how to pass the content of a variable that is on a class, specifically the gRPC GreeterService Class to the Blazor page when new information arrives. Notice that my aplication is a client and a server, and i make an initial comunication for the server and then the server starts to send to the client data(numbers) in unary mode, every time it has new data to send. I have all this working, but now i'm left it that final implementation.
This is my Blazor page
#page "/greeter"
#inject GrpcService1.GreeterService GreeterService1
#using BlazorApp1.Data
<h1>Grpc Connection</h1>
<input type="text" #bind="#myID" />
<button #onclick="#SayHello">SayHello</button>
<p>#Greetmsg</p>
<p></p>
#code {
string Name;
string Greetmsg;
async Task SayHello()
{
this.Greetmsg = await this.GreeterService1.SayHello(this.myID);
}
}
The method that later receives the communication from the server if the hello is accepted there is something like this:
public override async Task<RequestResponse> GiveNumbers(BalconyFullUpdate request, ServerCallContext context)
{
RequestResponse resp = new RequestResponse { RequestAccepted = false };
if (request.Token == publicAuthToken)
{
number = request.Number;
resp = true;
}
return await Task.FromResult(resp);
}
Every time that a new number arrives i want to show it in the UI.
Another way i could do this was, within a while condition, i could do a call to the server requesting a new number just like the SayHello request, that simply awaits for a server response, that only will come when he has a new number to send. When it comes the UI is updated. I'm just reluctant to do it this way because i'm afraid that for some reason the client request is forgotten and the client just sit's there waiting for a response that will never come. I know that i could implement a timeout on the client side to handle that, and on the server maybe i could pause the response, with a thread pause or something like that, and when the method that generates the new number has a new number, it could unpause the response to the client(no clue on how to do that). This last solution looks to me much more difficult to do than the first one.
What are your thoughts about it? And solutions..
##################### UPDATE ##########################
Now i'm trying to use a singleton, grab its instance in the Blazor page, and subcribe to a inner event of his.
This is the singleton:
public class ThreadSafeSingletonString
{
private static ThreadSafeSingletonString _instance;
private static readonly object _padlock = new object();
private ThreadSafeSingletonString()
{
}
public static ThreadSafeSingletonString Instance
{
get
{
if (_instance == null)
{
lock(_padlock)
{
if (_instance == null)
{
_instance = new ThreadSafeSingletonString();
_instance.number="";
}
}
}
return _instance;
}
set
{
_instance.number= value.number;
_instance.NotifyDataChanged();
}
}
public int number{ get; set; }
public event Action OnChange;
private void NotifyDataChanged() => OnChange?.Invoke();
And in Blazor page in code section i have:
protected override void OnInitialized()
{
threadSafeSingleton.OnChange += updateNumber();
}
public System.Action updateNumber()
{
this.fromrefresh = threadSafeSingleton.number + " que vem.";
Console.WriteLine("Passou pelo UpdateNumber");
this.StateHasChanged();
return StateHasChanged;
}
Unfortunatly the updatenumber function never gets executed...
To force a refresh of the ui you can call the StateHasChanged() method on your component:
https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.components.componentbase.statehaschanged?view=aspnetcore-3.1
Notifies the component that its state has changed. When applicable, this will cause the component to be re-rendered.
Hope this helps
Simple Request
After fully understanding that your problem is just to Update the Page not to get unsyncronous messages from the server with a bi directional connection. So jou just have to change your page like (please not there is no need to change the files generated by gRPC, I called it Number.proto so my service is named NumberService):
async Task SayHello()
{
//Request via gRPC
var channel = new Channel(Host + ":" + Port, ChannelCredentials.Insecure);
var client = new this.NumberService.NumberServiceClient(channel);
var request = new Number{
identification = "ABC"
};
var result = await client.SendNumber(request).RequestAccepted;
await channel.ShutdownAsync();
//Update page
this.Greetmsg = result;
InvokeAsync(StateHasChanged);//Required to refresh page
}
Bi Directional
For making a continious bi directional connection you need to change the proto file to use streams like:
service ChatService {
rpc chat(stream ChatMessage) returns (stream ChatMessageFromServer);
}
This Chant sample is from the https://github.com/meteatamel/grpc-samples-dotnet
The main challenge on this is do divide the task waiting for the gRPC server from the client. I found out that BackgroundService is good for this. So create a Service inherited from BackgroundService where place the while loop waiting for the server in the ExecuteAsyncmethod. Also define a Action callback to update the page (alternative you can use an event)
public class MyChatService : BackgroundService
{
Random _random = new Random();
public Action<int> Callback { get; set; }
protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
while (!stoppingToken.IsCancellationRequested)
{
// Replace next lines with the code request and wait for server...
using (_call = _chatService.chat())
{
// Read messages from the response stream
while (await _call.ResponseStream.MoveNext(CancellationToken.None))
{
var serverMessage = _call.ResponseStream.Current;
var otherClientMessage = serverMessage.Message;
var displayMessage = string.Format("{0}:{1}{2}", otherClientMessage.From, otherClientMessage.Message, Environment.NewLine);
if (Callback != null) Callback(displayMessage);
}
// Format and display the message
}
}
}
}
On the page init and the BackgroundService and set the callback:
#page "/greeter"
#using System.Threading
<p>Current Number: #currentNumber</p>
#code {
int currentNumber = 0;
MyChatService myChatService;
protected override async Task OnInitializedAsync()
{
myChatService = new MyChatService();
myChatService.Callback = i =>
{
currentNumber = i;
InvokeAsync(StateHasChanged);
};
await myChatService.StartAsync(new CancellationToken());
}
}
More information on BackgroundService in .net core can be found here: https://gunnarpeipman.com/dotnet-core-worker-service/
I am using .NET 4.5.2 for a web application and I have a HTTP handler that returns a processed image. I am making async calls to the process handler using jQuery and i have started getting the following error:
An asynchronous operation cannot be started at this time. Asynchronous operations may only be started within an asynchronous handler or module or during certain events in the Page lifecycle. If this exception occurred while executing a Page, ensure that the Page is marked <%# Page Async="true" %>. This exception may also indicate an attempt to call an "async void" method, which is generally unsupported within ASP.NET request processing. Instead, the asynchronous method should return a Task, and the caller should await it.
This is the handler code:
public void ProcessRequest(HttpContext context)
{
string CaseID = context.Request.QueryString["CaseID"].ToString();
int RotationAngle = Convert.ToInt16(context.Request.QueryString["RotationAngle"].ToString());
string ImagePath = context.Request.QueryString["ImagePath"].ToString();
applyAngle = RotationAngle;
string ImageServer = ConfigurationManager.AppSettings["ImageServerURL"].ToString();
string FullImagePath = string.Format("{0}{1}", ImageServer, ImagePath);
WebClient wc = new WebClient();
wc.DownloadDataCompleted += wc_DownloadDataCompleted;
wc.DownloadDataAsync(new Uri(FullImagePath));
}
private void wc_DownloadDataCompleted(object sender, DownloadDataCompletedEventArgs e)
{
Stream BitmapStream = new MemoryStream(e.Result);
Bitmap b = new Bitmap(BitmapStream);
ImageFormat ImageFormat = b.RawFormat;
b = RotateImage(b, applyAngle, true);
using (MemoryStream ms = new MemoryStream())
{
if (ImageFormat.Equals(ImageFormat.Png))
{
HttpContext.Current.Response.ContentType = "image/png";
b.Save(ms, ImageFormat.Png);
}
if (ImageFormat.Equals(ImageFormat.Jpeg))
{
HttpContext.Current.Response.ContentType = "image/jpg";
b.Save(ms, ImageFormat.Jpeg);
}
ms.WriteTo(HttpContext.Current.Response.OutputStream);
}
}
Any idea what this means and I could do to overcome this?
Thanks in advance.
You code won't work as it is, because you create a WebClient inside the ProcessRequest method but don't wait for it to finish. As a result, the client will be orphaned as soon as the method finishes. By the time a response arrives, the request itself has finished. There is no context or output stream to which you can write the response.
To create an asynchronous HTTP Handler you need to derive from the HttpTaskAsyncHandler class and implement the ProcessRequestAsync method:
public class MyImageAsyncHandler : HttpTaskAsyncHandler
{
public override async Task ProcessRequestAsync(HttpContext context)
{
//...
using(WebClient wc = new WebClient())
{
var data=await wc.DownloadDataTaskAsync(new Uri(FullImagePath));
using(var BitmapStream = new MemoryStream(data))
{
//...
ms.WriteTo(context.Response.OutputStream);
//...
}
}
}
}
I have an asp.net webforms application and to retrieve video from database that saved in varbinary format and show it as html5 video tag.
after a googled it, i found a way that i should play it asynchronously using ASP.Net WebApi, it works fine
First problem
When video played first time and the user click on play button to replay the video, The remote host closed the connection. The error code is 0x800704CD exception throws at line await outputStream.WriteAsync(buffer, 0, bytesRead);.
Second Problem
When user click on seek bar, the video goes to played from first.
NOTE
Internet Explorer 11 plays the video without any problem, but firefox and chrome have both problems.
how can i solve this problem?
Here is my codes:
public static class WebApiConfig
{
public static void Register(HttpConfiguration config)
{
config.EnableCors();
config.MapHttpAttributeRoutes();
config.Routes.MapHttpRoute(
name: "VideoApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
}
}
public class VideoController : ApiController
{
public IVideoRepository videoRepository;
public HttpResponseMessage Get(long id)
{
try
{
videoRepository = new VideoRepository();
Video video = videoRepository.load(id);
if (video != null)
{
var videoStream = new VideoStream(video.fileContent);
string ext = video.extension;
var response = Request.CreateResponse();
response.Content = new PushStreamContent((Action<Stream, HttpContent, TransportContext>)videoStream.WriteToStream, new MediaTypeHeaderValue("video/" + ext));
response.Content.Headers.Add("Content-Disposition", "attachment;filename=" + video.fullName.Replace(" ", ""));
response.Content.Headers.Add("Content-Length", videoStream.FileLength.ToString());
return response;
}
else
{
return Request.CreateResponse(HttpStatusCode.NotFound);
}
}
catch (Exception e)
{
return Request.CreateErrorResponse(HttpStatusCode.ServiceUnavailable, e);
}
}
}
public class VideoStream
{
private readonly byte[] _fileContent;
private long _contentLength;
public long FileLength
{
get { return _contentLength; }
}
public VideoStream(byte[] content)
{
_contentLength = content.Length;
_fileContent = content;
}
public async void WriteToStream(Stream outputStream, HttpContent content, TransportContext context)
{
try
{
var buffer = new byte[65536];
MemoryStream memoryStream = new MemoryStream();
memoryStream.Write(_fileContent, 0, _fileContent.Length);
memoryStream.Position = 0;
using (memoryStream)
{
var length = (int)memoryStream.Length;
var bytesRead = 1;
while (length > 0 && bytesRead > 0)
{
bytesRead = memoryStream.Read(buffer, 0, Math.Min(length, buffer.Length));
await outputStream.WriteAsync(buffer, 0, bytesRead);
length -= bytesRead;
}
}
}
catch (Exception e)
{
throw e;
}
finally
{
outputStream.Close();
}
}
}
UPDATE
after this way didn't worked properly, i had to use this way, but the new way have seekbar problem, when user click on seek bar to seek to time it dosn't work in Chrome and FireFox.
ASP.NET is not very good at video streaming. Third-party video streaming solution is the best option.
There are a few video-streaming servers (like Wowza), but they require installation and you have to buy license.
Cloud streaming service is another option. I personally prefer AWS Cloudfront. They propose distribution in various globally distributed content delivery zones. It costs really cheap and you can be sure that it will survive any traffic amount (even if all your users will watch the same video simultaneously).
You might have got the answer by now. But this might help others-
My best bet is removing the Content-length from the response headers.
Content-Length tells the caller that it needs to receive this fixed length in the response.
When you click on a play button, the complete video stream is not received (i.e., the entire Content-Length is not received.) & therefore, the error.
Another approach could be using response.Headers.TransferEncodingChunked = true, which tells the caller that it will receive a response in chunks. The only catch here is you will get a 200OK even if the stream is not present.
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 have been experimenting with WP7 apps today and have hit a bit of a wall.
I like to have seperation between the UI and the main app code but Ive hit a wall.
I have succesfully implemented a webclient request and gotten a result, but because the call is async I dont know how to pass this backup to the UI level. I cannot seem to hack in a wait for response to complete or anything.
I must be doing something wrong.
(this is the xbox360Voice library that I have for download on my website: http://www.jamesstuddart.co.uk/Projects/ASP.Net/Xbox_Feeds/ which I am porting to WP7 as a test)
here is the backend code snippet:
internal const string BaseUrlFormat = "http://www.360voice.com/api/gamertag-profile.asp?tag={0}";
internal static string ResponseXml { get; set; }
internal static WebClient Client = new WebClient();
public static XboxGamer? GetGamer(string gamerTag)
{
var url = string.Format(BaseUrlFormat, gamerTag);
var response = GetResponse(url, null, null);
return SerializeResponse(response);
}
internal static XboxGamer? SerializeResponse(string response)
{
if (string.IsNullOrEmpty(response))
{
return null;
}
var tempGamer = new XboxGamer();
var gamer = (XboxGamer)SerializationMethods.Deserialize(tempGamer, response);
return gamer;
}
internal static string GetResponse(string url, string userName, string password)
{
if (!string.IsNullOrEmpty(userName) && !string.IsNullOrEmpty(password))
{
Client.Credentials = new NetworkCredential(userName, password);
}
try
{
Client.DownloadStringCompleted += ClientDownloadStringCompleted;
Client.DownloadStringAsync(new Uri(url));
return ResponseXml;
}
catch (Exception ex)
{
return null;
}
}
internal static void ClientDownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
if (e.Error == null)
{
ResponseXml = e.Result;
}
}
and this is the front end code:
public void GetGamerDetails()
{
var xboxManager = XboxFactory.GetXboxManager("DarkV1p3r");
var xboxGamer = xboxManager.GetGamer();
if (xboxGamer.HasValue)
{
var profile = xboxGamer.Value.Profile[0];
imgAvatar.Source = new BitmapImage(new Uri(profile.ProfilePictureMiniUrl));
txtUserName.Text = profile.GamerTag;
txtGamerScore.Text = int.Parse(profile.GamerScore).ToString("G 0,000");
txtZone.Text = profile.PlayerZone;
}
else
{
txtUserName.Text = "Failed to load data";
}
}
Now I understand I need to place something in ClientDownloadStringCompleted but I am unsure what.
The problem you have is that as soon as an asynchronous operation is introduced in to the code path the entire code path needs to become asynchronous.
Because GetResponse calls DownloadStringAsync it must become asynchronous, it can't return a string, it can only do that on a callback
Because GetGamer calls GetResponse which is now asynchronous it can't return a XboxGamer, it can only do that on a callback
Because GetGamerDetails calls GetGamer which is now asynchronous it can't continue with its code following the call, it can only do that after it has received a call back from GetGamer.
Because GetGamerDetails is now asynchronous anything call it must also acknowledge this behaviour.
.... this continues all the way up to the top of the chain where a user event will have occured.
Here is some air code that knocks some asynchronicity in to the code.
public static void GetGamer(string gamerTag, Action<XboxGamer?> completed)
{
var url = string.Format(BaseUrlFormat, gamerTag);
var response = GetResponse(url, null, null, (response) =>
{
completed(SerializeResponse(response));
});
}
internal static string GetResponse(string url, string userName, string password, Action<string> completed)
{
WebClient client = new WebClient();
if (!string.IsNullOrEmpty(userName) && !string.IsNullOrEmpty(password))
{
client.Credentials = new NetworkCredential(userName, password);
}
try
{
client.DownloadStringCompleted += (s, args) =>
{
// Messy error handling needed here, out of scope
completed(args.Result);
};
client.DownloadStringAsync(new Uri(url));
}
catch
{
completed(null);
}
}
public void GetGamerDetails()
{
var xboxManager = XboxFactory.GetXboxManager("DarkV1p3r");
xboxManager.GetGamer( (xboxGamer) =>
{
// Need to move to the main UI thread.
Dispatcher.BeginInvoke(new Action<XboxGamer?>(DisplayGamerDetails), xboxGamer);
});
}
void DisplayGamerDetails(XboxGamer? xboxGamer)
{
if (xboxGamer.HasValue)
{
var profile = xboxGamer.Value.Profile[0];
imgAvatar.Source = new BitmapImage(new Uri(profile.ProfilePictureMiniUrl));
txtUserName.Text = profile.GamerTag;
txtGamerScore.Text = int.Parse(profile.GamerScore).ToString("G 0,000");
txtZone.Text = profile.PlayerZone;
}
else
{
txtUserName.Text = "Failed to load data";
}
}
As you can see async programming can get realy messy.
You generally have 2 options. Either you expose your backend code as an async API as well, or you need to wait for the call to complete in GetResponse.
Doing it the async way would mean starting the process one place, then return, and have the UI update when data is available. This is generally the preferred way, since calling a blocking method on the UI thread will make your app seem unresponsive as long as the method is running.
I think the "Silverlight Way" would be to use databinding. Your XboxGamer object should implement the INotifyPropertyChanged interface. When you call GetGamer() it returns immediately with an "empty" XboxGamer object (maybe with GamerTag=="Loading..." or something). In your ClientDownloadStringCompleted handler you should deserialize the returned XML and then fire the INotifyPropertyChanged.PropertyChanged event.
If you look at the "Windows Phone Databound Application" project template in the SDK, the ItemViewModel class is implemented this way.
Here is how you can expose asynchronous features to any type on WP7.