通过 SignalR 从 Web API 向连接的客户端发布消息答案

【问题标题】：Publish message to connected clients from Web API through SignalR通过 SignalR 从 Web API 向连接的客户端发布消息
【发布时间】：2022-02-14 14:14:47
【问题描述】：

目前我有我的服务器端 Web 应用程序来创建一个客户端来调用我的 Web API 端点，它将消息适当地发布回 Web 应用程序（客户端）。

我的想法是，是否可以使用 Postman 触发 Web API 端点，然后所有连接的客户端都会收到该任务正在执行的消息。

我的端点

public class DailyPostingController : ControllerBase
{
    private readonly IMapper _mapper;
    private readonly IDailyPostingService _DailyPostingService;
    private readonly ILogger<DailyPostingController> _logger;

    public DailyPostingController(IMapper mapper, 
        IDailyPostingService DailyPostingService, 
        ILogger<DailyPostingController> logger)
    {
        _mapper = mapper;
        _DailyPostingService = DailyPostingService;
        _logger = logger;
    }

    [Authorize(Policy = Permissions.DailyPosting.Execute)]
    [HttpPost("Execute")]
    [ProducesResponseType(StatusCodes.Status200OK)]
    [ProducesResponseType(StatusCodes.Status400BadRequest)]
    public async Task<int> Execute(OperatingCentreQueryModel ocQueryModel)
    {
        _logger.LogDebug("Executing Daily posting for date#" 
            + ocQueryModel.ProcessDate.ToString("dd/mmm/yyy"));

        //How to trigger the hub to tell connected clients this process is started?
        var res = await _DailyPostingService.Execute(ocQueryModel);
        //How to trigger the hub to tell connected clients this process was done?
        return res;
    }
}

我的中心

public class NotificationHub : Hub<INotificationHub>
{
    private readonly UsersState _usersState;
    private readonly ProcessState _processState;
    private readonly ILogger<NotificationHub> _logger;

    public NotificationHub(UsersState usersState, ProcessState processState,
        ILogger<NotificationHub> logger)
    {
        _usersState = usersState;
        _processState = processState;
        _logger = logger;
    }

    public async Task SendMessage(string user, string message)
    {
        await Clients.All.ReceiveMessage(user, message);
    }

    public async Task SendMessageToCaller(string user, string message)
    {
        await Clients.Caller.ReceiveMessage(user, message);
    }

    public async Task SendMessageToGroup(string user, string group, string message)
    {
        await Clients.Group(group).ReceiveMessage(user, message);
    }

    public override Task OnConnectedAsync()
    {
        LogDebug($"({Context.ConnectionId}) connected to notification hub.");
        return base.OnConnectedAsync();
    }

    public override async Task OnDisconnectedAsync(Exception exception)
    {
        LogDebug($"({Context.ConnectionId}) disconnected to notification hub.");
        _usersState.RemoveConnectionId(Context.ConnectionId,
            async (user) =>
            {
                await RemoveUser(user);
                await RemoveUserProcess(user);
            });

        await base.OnDisconnectedAsync(exception);
    }

    private void LogDebug(string msg)
    {
        _logger.LogDebug("*** " + msg);
    }

【问题讨论】：

标签： signalr asp.net-core-webapi signal-processing signalr-hub

【解决方案1】：

文档描述了如何做到这一点https://docs.microsoft.com/aspnet/core/signalr/hubcontext?view=aspnetcore-6.0

【讨论】：

【解决方案2】：

您可以使用 IHubContext 服务从应用中的其他位置发送 SignalR 消息。您只需将其注入您需要使用它的地方。

为了解决您的问题，我将向 INotificationHub 添加一个新方法：

public interface INotificationHub
{
    Task ExcecutingDailyPost(string action);
}

在需要使用集线器功能的任何地方注入强类型集线器上下文。

您的端点可能如下所示：

public class DailyPostingController : ControllerBase
{
    private readonly IMapper _mapper;
    private readonly IDailyPostingService _DailyPostingService;
    private readonly ILogger<DailyPostingController> _logger;
    private readonly IHubContext<NotificationHub, INotificationHub> _hubContext;

    public DailyPostingController(IMapper mapper, 
        IDailyPostingService DailyPostingService, 
        ILogger<DailyPostingController> logger,
        IHubContext<NotificationHub, INotificationHub> hubContext)
    {
        _mapper = mapper;
        _DailyPostingService = DailyPostingService;
        _logger = logger;
        _hubContext = hubContext;
    }

    [Authorize(Policy = Permissions.DailyPosting.Execute)]
    [HttpPost("Execute")]
    [ProducesResponseType(StatusCodes.Status200OK)]
    [ProducesResponseType(StatusCodes.Status400BadRequest)]
    public async Task<int> Execute(OperatingCentreQueryModel ocQueryModel)
    {
        _logger.LogDebug("Executing Daily posting for date#" 
            + ocQueryModel.ProcessDate.ToString("dd/mmm/yyy"));
        
        // Notify your clients that the process has started
        await _hubContext.Clients.All.ExcecutingDailyPost("START");

        var res = await _DailyPostingService.Execute(ocQueryModel);

        // Notify your clients that the process has ended
        await _hubContext.Clients.All.ExcecutingDailyPost("END");
        return res;
    }
}

然后在客户端，您需要在“ExcecutingDailyPost”频道上收听，并根据操作，做您想做的事。

【讨论】：