在ASP.NET Core 中使用SignalR

    private readonly ILogger<ServerHub> \_logger;  
    private ISysUser \_userService = null;  
    private readonly IHttpContextAccessor \_accessor;

    public ServerHub(ISysUser user, ILogger<ServerHub> logger, IHttpContextAccessor accessor)  
    {  
        \_userService = user;  
        \_logger = logger;  
        \_accessor = accessor;  
    }

    /// <summary>  
    /// 当连接成功时执行  
    /// </summary>  
    /// <returns></returns>  
    public override Task OnConnectedAsync()  
    {  
        string connId = Context.ConnectionId;

        \_logger.LogWarning("SignalR已连接");  
        //验证Token  
        var token= \_accessor.HttpContext.Request.Query\["access\_token"\];  
        var user = JwtHelper.SerializeJwt(token);  
        \_logger.LogWarning("SignalR已连接，用户名：" + user.UserName);  
        //连接用户 这里可以存在Redis  
        var model= new UserModel  
        {  
            ConnectionId = connId,  
            Token = token,  
            UserName = user.UserName  
        };  
        OnlineUser.Add(model);  
        //给当前的连接分组 可以进行同一组接收消息 也可以用Token获取机构权限  
        //await Groups.AddToGroupAsync(Context.ConnectionId, "测试组");

        //给当前连接返回消息 .Clients可以发多个连接ID  
        Clients.Client(connId).SendAsync("ConnectResponse",  
            new ApiResult<UserModel>()  
            {  
                state=200,  
                data = model,  
                msg= user.UserName+"连接成功"  
            });

        return base.OnConnectedAsync();  
    }

    /// <summary>  
    /// 当连接断开时的处理  
    /// </summary>  
    public override Task OnDisconnectedAsync(Exception exception)  
    {  
        string connId = Context.ConnectionId;  
        var model = OnlineUser.Find(u => u.ConnectionId == connId);  
        int count = OnlineUser.RemoveAll(u => u.ConnectionId == connId);  
        if (model != null)  
        {  
            //给当前分组发送消息 在一个分组就能接收到消息  
            //Clients.Group(model.GroupName).SendAsync("GetUsersResponse", result);

            //给当前连接返回消息 .Clients可以发多个连接ID  
            Clients.Client(connId).SendAsync("DisconnectResponse",  
            new ApiResult<bool>()  
            {  
                state = 1000,  
                data = true,  
                msg = "断开连接"  
            });

        }  
        return base.OnDisconnectedAsync(exception);  
    }

    /// <summary>  
    /// 接受用户的数进行推送  
    /// </summary>  
    /// <returns></returns>  
    public async Task SendMessage(string user,string msg)  
    {  
        ApiResult<UserModel> result = new ApiResult<UserModel>();  
        result.data = new UserModel  
        {  
            ConnectionId = Context.ConnectionId,  
            Token = "",  
            UserName = user  
        };  
        result.state = 200;  
        result.msg = msg;

        //推送给所有连接ID的第一条数据  
        await Clients.Clients(OnlineUser.Select(q=>q.ConnectionId).ToList()).SendAsync("SendMessage", result);  
    }

}

在Startup里注册SignalR:

注意 如果报跨域错误

endpoints.MapHub("/serverHub").RequireCors(t => t.WithOrigins(new string[] { "http://localhost:8080" }).AllowAnyMethod().AllowAnyHeader().AllowCredentials());

我这里定时像前台推送数据  实际项目可以用MQ

///

    public async Task Execute(IJobExecutionContext context)  
    {  
        ApiResult<bool> result = new ApiResult<bool>();  
        if (ServerHub.OnlineUser.Count == 0)  
        {  
            result.data = false;  
            result.state = 1000;  
            result.msg = "没有连接用户";  
        }  
        else  
        {  
            result.data = true;  
            result.state = 200;  
            result.msg = "推送第一条数据";  
        }

        //推送给所有连接ID的第一条数据  
        await \_hubContext.Clients.Clients(ServerHub.OnlineUser.Select(q => q.ConnectionId).ToList()).SendAsync("SendMessageResponse", result);  
    }  
}