从控制器ASP.NET Core 2.1到特定客户端的SignalR调用 [英] SignalR call to specific client from controller ASP.NET Core 2.1

问题描述

用户在浏览器中提交表单后，我需要从服务器向客户端发送即时消息.

I need to send an instant message from the server to the client after the user has submitted a form in a browser.

我按照Microsoft的步骤

I followed the Microsoft steps here to set up a signalR connection, created a Hub class, signalr.js etc.

问题是我只能向所有客户端调用一条消息，但是我需要向发起请求的特定调用者调用该消息(否则每个人都会收到该消息).

The problem is that I can only invoke a message to all clients, but I need to invoke the message to the specific caller who initiated the request (otherwise everyone will get the message).

这是我在HomeController.cs中的POST操作:

This is my POST Action in the HomeController.cs:

[HttpPost]
    [ValidateAntiForgeryToken]
    public async Task<IActionResult> Submit(string signalRconnectionId, Dictionary<string, string> inputs)
    {
        //Invoke signal to all clients sending a message to initSignal WORKS FINE
        await _signalHubContext.Clients.All.SendAsync("initSignal", "This is a message from the server!");

        //Invoke signal to specified client where signalRConnectionId = connection.id DOES NOT WORK
        await _signalHubContext.Clients.Client(signalRconnectionId).SendAsync("initSignal", "This is a message from server to this client: " + signalRconnectionId);

        return RedirectToAction("Success", inputs);
    }

我的客户端javascript文件:

my client javascript file:

    //Create connection and start it
const connection = new signalR.HubConnectionBuilder()
    .withUrl("/signalHub")
    .configureLogging(signalR.LogLevel.Information)
    .build();
connection.start().catch(err => console.error(err.toString()));

console.log("connectionID: " + connection.id);
$("#signalRconnectionId").attr("value", connection.id);

//Signal method invoked from server
connection.on("initSignal", (message) => {

    console.log("We got signal! and the message is: " + message);


});

我尝试调试该操作方法，并正确传入了"0"的connectionId(每个连接递增1)

I have tried debugging the action method and I get correctly passed in the connectionId which is "0" (incrementing by 1 per connection)

推荐答案

所以这是我从我通过从客户端调用Hub类，然后从客户端调用传入connectionId的控制器来获取connectionId.

I got the connectionId by calling the Hub class from client and then from client calling the controller passing in the connectionId.

补习班:

public class SignalHub : Hub
{


    public string GetConnectionId()
    {
        return Context.ConnectionId;
    }
}

在启动时执行的客户端javascript代码:

client-side javascript code executed at startup:

connection.start().catch(err => console.error(err.toString())).then(function(){
connection.invoke('getConnectionId')
    .then(function (connectionId) {
        // Send the connectionId to controller
        console.log("connectionID: " + connectionId);
        $("#signalRconnectionId").attr("value", connectionId);
    });

});

HomeController.cs:

HomeController.cs:

public async Task<IActionResult> Submit(string signalRconnectionId, Dictionary<string, string> inputs)
    {

        //Invoke signal to specified client WORKS NOW
        await _signalHubContext.Clients.Client(signalRconnectionId).SendAsync("initSignal", "This is a message from server to this client: " + signalRconnectionId);

        return RedirectToAction("Success", inputs);
    }

它可以正常工作，但仍然感觉像是往返，如果我们不必通过集线器类来实现此目的，那会更容易.也许只是从客户端开始具有connectionId，但是也许有充分的理由进行设计:)

It works fine, but still feels a little like a roundtrip, it would have been easier if we didn't have to go through the hub class to make this happen. Maybe just having the connectionId from the client-side to begin with, but maybe there is a good reason for the design :)

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