在 Hub 类之外调用 SignalR 函数

Question

1. 我正在尝试获取 Hub 类的实例，以从 Hub 类之外的类的后端调用前端方法。

2. 我正在使用具有注册功能的 IHostLifeTime，该功能将在服务器以 while 循环运行时在后台运行。

3. while循环中会有事件触发signalR向客户端发送消息。

问题：我应该如何访问集线器并向 ApplicationReady() 函数中的管理器类内部的客户端发送消息？

TestHub.cs：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.SignalR;

namespace SignalREventHandle
{
    public class TestHub : Hub
    {
        public async Task SendMessage(string user, string message)
        {
            Console.WriteLine($"user: {user} message:{message}");
            await Clients.All.SendAsync("ReceiveMessage", user, message);
        }

    }
}

Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.SignalR;
using System.Threading;

namespace SignalREventHandle
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

      // This method gets called by the runtime. Use this method to add services to the container.

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddRazorPages();
            services.AddSignalR();
        }

  // This method gets called by the runtime. Use this method to configure the HTTP request //pipeline.

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IHostApplicationLifetime lifetime, IHubContext<TestHub> hubContext)

        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Error");
            }

            lifetime.ApplicationStarted.Register(OnAppStarted);

            app.UseStaticFiles();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>

            {
                endpoints.MapRazorPages();

                endpoints.MapHub<TestHub>("/testHub");
            });
        }

        public async void OnAppStarted()

        {

            //Get Singleton Instance of Manager and then start the application
            var manager = Manager.Instance;
            manager.ApplicationReady();
        }

    }

}

Manager.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.AspNetCore.SignalR;

namespace SignalREventHandle

{
    public class Manager
    {
        private bool _isServerRunning;
 
        /// <summary>

        /// Instance of class to implement Singleton

        /// </summary>

        private static readonly Manager _instance = new();

        /// <summary>

        /// Getter for Class instance

        /// </summary>

        public static Manager Instance

        {
            get => _instance;
        }

 

        public async void ApplicationReady()
        {
            var task = Task.Run(() =>
            {
                _isServerRunning = true;

                while (_isServerRunning)

                {

                   // Want to Send Message to Client with SignalR here

                    Thread.Sleep(10000);
                }

            });

        }

    }
}

Answer 1

在 ASP.NET 4.x SignalR 中使用 GlobalHost 提供对 IHubContext 的访问：

public static async Task SendMessage(string user, string message)
{
    Console.WriteLine($"user: {user} message: {message}");

    // Get an instance of IHubContext from GlobalHost
    var hubContext = GlobalHost.ConnectionManager.GetHubContext<ChatHub>();
    await hubContext.Clients.All.SendAsync("ReceiveMessage", user, message);
}

在 ASP.NET Core SignalR 中，您可以从 Web 主机访问 IHubContext 的实例。

程序.cs

public class Program
{
    public static IHost WebHost;
    public static void Main(string[] args)
    {
        WebHost = CreateHostBuilder(args).Build();
        WebHost.Run();
    }
    ...
}

然后：

public static async Task SendMessage(string user, string message)
{
    Console.WriteLine($"user: {user} message: {message}");

    // Get an instance of IHubContext from IHost
    var hubContext = Program.WebHost.Services.GetService(typeof(IHubContext<ChatHub>)) as IHubContext<ChatHub>;
    await hubContext.Clients.All.SendAsync("ReceiveMessage", user, message);
}

文档：

• https://docs.microsoft.com/en-us/aspnet/core/signalr/hubcontext?view=aspnetcore-5.0
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