I'm following this guide: http://www.asp.net/signalr/overview/signalr-20/hubs-api/hubs-api-guide-net-client#callserver
I have the following:
_hubProxy = _hubConnection.CreateHubProxy("appHub");
_hubConnection.Start().Wait();
_hubProxy.Invoke("SendNavbarMessage", _hubConnection.ConnectionId).Wait();
Originally, I had a complex type being passed vie Invoke, but to debug I'm trying to use a parameterless hub method. My hub:
[HubName("appHub")]
public class AppHub : Hub {
// prep
public void SendNavbarMessage() {
// do stuff
}
}
When I call Invoke(), I see the following error:
{"'SendNavbarMessage' method could not be resolved."}
This is with Detailed error messages enabled in the signalR configuration... I get no other details.
What am I doing wrong?
Invoke sends one parameter to the method, but your Hub method has no parameters
_hubProxy.Invoke("SendNavbarMessage", _hubConnection.ConnectionId)
Should maybe be
_hubProxy.Invoke("SendNavbarMessage");
Related
I've scoured through the .NET documentation and cannot find what these strings representing methods mean. For instance "ReceiveMessage" and "SendMessage" in:
hubConnection = new HubConnectionBuilder();
...
hubConnection.On<string, string>("ReceiveMessage", ..);
and
await hubConnection.SendAsync("SendMessage", userInput, messageInput);
are some examples. I realize in the Hub we have methods that can be these names, but sometimes not? For the toy example I'm using from the .NET documentation, a ChatHub class is defined as follows:
public class ChatHub : Hub
{
public async Task SendMessage(string user, string message)
{
await Clients.All.SendAsync("ReceiveMessage", user, message);
}
}
So here I can see the "SendMesage" method exists. But nowhere is there any "ReceiveMessage" method in the source code. I'm a bit disappointed the documentation doesn't actually explain what these strings representing functions mean in any detail. Do they represent javascript functions? Only locally defined functions in C# (then where is ReceiveMessage?)? Globally defined functions in SignalR? What are they?
They refer to methods on the client.
I guess the exact details vary between languages, but here is one simple example in Dart/Flutter using the signalr_netcore package:
In your server code
// Call the TestMethod method on the client
await Clients.Caller.SendAsync("TestMethod", "some arguments from the server");
In your client code
hub.on('TestMethod', (arguments) async {
print('TestMethod called from server with $arguments');
});
The above code will print TestMethod called from server with [some arguments from the server].
I want to send messages from the server (from a class, not a controller) via the SignalR Hub.
The hub works for messages originating from the client but not for messages from the server.
I've tried multiple methods of which non seem to work. For example, I tried retrieving the hub context using:
GlobalHost.ConnectionManager.GetHubContext<MyHub>()
with no success.
What is the best and up-to-date method of doing this in .NET Core?
Temporary Solution:
Having a websocket client inside the host api. Then making it connect to itself. This is not an ideal solution but works as a temporary fix.
You can inject the context in your class as service. Your class must be initialized via DI and added as a service. There is no difference between class or controller.
public class SomeClass
{
public IHubContext<ChatHub, IChatClient> _strongChatHubContext { get; }
public SomeClass(IHubContext<ChatHub, IChatClient> chatHubContext)
{
_strongChatHubContext = chatHubContext;
}
public async Task SendMessage(string message)
{
await _strongChatHubContext.Clients.All.ReceiveMessage(message);
}
}
You can also get service like following by injecting IHttpContextAccessor
var _strongChatHubContext = httpContextAccessor.HttpContext.RequestServices.GetRequiredService<IHubContext<ChatHub, IChatClient>>()
reference:
https://learn.microsoft.com/en-us/aspnet/core/signalr/hubcontext?view=aspnetcore-2.1
First you need to somewhere instantiate your hub (normally when your app is bootstrapping).
MyHub myHub = new MyHub();
Then on your class inject the context:
private readonly IHubContext<NotifyHub, ITypedHubClient> hubContext;
And in your class method just call the hub:
hubContext.Clients.All.yourHubMethod(yourPayload);
I have my signalr running on a separate domain. We will have multiple applications using it to send and receive messages. I created the connection and hub proxy using the following code
connection = $.hubConnection("https://someurl.com", { useDefaultPath: false });
chatHub = connection.createHubProxy('chatHub');
I can get messages from the server sent to the client using the following code which works fine
chatHub.on('receiveEntityMessage', function (chatMessage) {
if (chatMessage) {
console.log(chatMessage.Message);
}
});
Now I dont know how to call server functions with parameters from the client. Can anybody please help me with this?
chatHub.invoke("MethodName", param1, param2, param3).done(function(result) {
console.log(result);
});
Since i'm not sure what is the language of your server side, i am going to provide a C# example.
C# Hub method example:
public class chatHub: Hub {
public void YourHubMehotd(int firstParam, string secondParam){
//The action of your method
}
}
JS client side:
You can call your hub method like this:
{The variable with the hub connection}.server.{the method you want to call}( {the parameters} )
Example:
chatHub.server.YourHubMehotd(1,"Example");
I recomend to create a js function to call the hub method.
function callMyHubMethod(firstParam, secondParam){
chatHub.server.YourHubMehotd(firstParam, secondParam);
}
My web api looks like:
[Route("api/[controller]")]
public class ValuesController : Controller
{
private readonly ApplicationDbContext _context;
public ValuesController(ApplicationDbContext context)
{
_context = context;
}
[HttpGet]
public string Get()
{
// get random user
var user = _context.Users.SingleOrDefault();
return user?.Email ?? "";
}
}
Trying to call it via jquery:
$.get('/api/values', function (email) {
console.log(email)
})
I've 2 questions:
1/. Why didn't console.log(email) work although I was getting the response successful?
There was nothing in the Console tab.
2/. When I made a request to server (/api/values), the breakpoint had been caught:
My question: where had ValuesController been called within context? I'd sent a request from client, then the constructor was hit (I'm sure that I didn't send something like ApplicationDbContext from client to server :v)
UPDATE: By changing $.get('/api/values', {}, function (email) {} to $.get('/api/values', function (email) {}. I've fixed the first problem. It's my bad. Sorry about that.
Shorter Answer
My question: where had ValuesController been called within context? I'd sent a request from client, then the constructor was hit.
The HTTP Request arrived. ASP.NET MVC Routing told the application to use the ValuesController to handle the request. The application constructed the ValuesController, supplying an instance of ApplicationDbContext via dependency injection.
Longer Answer
The Startup.Configure method is used to specify how the ASP.NET application will respond to individual HTTP requests. Since you are using Web API, you have configured app.UseMvc(). Result: when an HTTP Request arrives, MVC Routing tells the application to use the appropriate controller.
The Startup.ConfigureServices method is used to specify services that are available via dependency injection. Since you are injecting an ApplicationDbContext into your constructor, you have configured services.AddDbContext<ApplicationDbContext>(). Result: when the application constructs a ValuesController, ASP.NET Dependency Injection will provide an instance of the ApplicationDbContext.
I've developed a sample SignalR application based on ASP.NET 4.5 & Owin, and I've hosted that app on IIS 7.5.
Everything is working fine, but how can I handle exceptions in Owin?
Consider the following code:
[HubName("SampleHub")]
public class SampleHub : Hub
{
public SampleHub()
{
throw new InvalidOperationException("?!");
}
}
This exception won't call Application_Error (and this is my problem).
Where can I get all exceptions from Owin for logging and debugging purposes similarly to Application_Error?
I'm not interested in something like this:
app.UseErrorPage(new ErrorPageOptions()
{
ShowCookies = true,
ShowEnvironment = true,
ShowExceptionDetails = true,
ShowHeaders = true,
ShowQuery = true,
ShowSourceCode = true
});
This is totally useless for advanced scenarios, something like ASP.NET Web API and ASP.NET MVC.
Action filters with OnException method for override purposes is much better.
If you want exception handling specifically for SignalR Hubs, OWIN middleware is not the way to go.
To illustrate just one reason why, suppose that SignalR is using its WebSocket transport when an exception is thrown from inside a Hub method. In this case, SignalR will not close the WebSocket connection. Instead SignalR will write a JSON encoded message directly to the socket to indicate to the client that an exception was thrown. There is no easy way using OWIN middleware to trigger any sort of event when this happens outside of possibly wrapping the entire OWIN WebSocket Extension which I would strongly advise against.
Fortunately SignalR provides its own Hub Pipeline which is perfectly suited for your scenario.
using System;
using System.Diagnostics;
using Microsoft.AspNet.SignalR.Hubs;
public class MyErrorModule : HubPipelineModule
{
protected override void OnIncomingError(ExceptionContext exceptionContext, IHubIncomingInvokerContext invokerContext)
{
MethodDescriptor method = invokerContext.MethodDescriptor;
Debug.WriteLine("{0}.{1}({2}) threw the following uncaught exception: {3}",
method.Hub.Name,
method.Name,
String.Join(", ", invokerContext.Args),
exceptionContext.Error);
}
}
You can use the ExceptionContext for more than just logging. For example you can set ExceptionContext.Error to a different exception which will change the exception the client receives.
You can even suppress the exception by setting ExceptionContext.Error to null or by setting ExceptonContext.Result. If you do this, It will appear to the client that the Hub method returned the value you found in ExceptonContext.Result instead of throwing.
A while back a wrote another SO answer about how you can call a single client callback for every exception thrown by a Hub method: SignalR exception logging?
There is also MSDN documentation for HubPipelineModules: http://msdn.microsoft.com/en-us/library/microsoft.aspnet.signalr.hubs.hubpipelinemodule(v=vs.118).aspx
The answer by #halter73 is great for errors thrown inside hubs, but it doesn't catch errors thrown during their creation.
I was getting the exception:
System.InvalidOperationException: 'foobarhub' Hub could not be resolved.
The server was returning an HTML page for this exception, but I needed it in JSON format for better integration with my Angular app, so based on this answer I implemented an OwinMiddleware to catch exceptions and change the output format. You could use this for logging errors instead.
public class GlobalExceptionMiddleware : OwinMiddleware
{
public GlobalExceptionMiddleware(OwinMiddleware next)
: base(next)
{
}
public override async Task Invoke(IOwinContext context)
{
try
{
await Next.Invoke(context);
}
catch (Exception ex)
{
context.Response.ContentType = "application/json";
context.Response.StatusCode = 500;
await context.Response.WriteAsync(JsonConvert.SerializeObject(ex));
}
}
}
Add the registration in OwinStartup.cs, just remember to place it before the MapSignalR method call:
public class OwinStartup
{
public void Configuration(IAppBuilder app)
{
app.Use<GlobalExceptionMiddleware>(); // must come before MapSignalR()
app.MapSignalR();
}
}