c# - 如何向 NET Core 2.0 的 SignalR alpha 上的所有客户端发送消息

Question

我正在使用 signalR 1.0.0-alpha2-final 并想向所有连接的客户端发送消息。

我用过this tutorial作为起点。

我的 RulesHub 继承自 Hub:

[EnableCors("MyPolicy")]
public class RulesHub : Hub
{
    private readonly IRuleService _ruleService;

    public RulesHub(IRuleService ruleService)
    {
        _ruleService = ruleService;
    }

    public Task Send()
    {
        var rules = _ruleService.RulesMonitoring();
        return Clients.All.InvokeAsync("SendRules", rules);
    }
}

在前端我有这个代码来连接到集线器:

let connection = new signalR.HubConnection(rulesMonitorUrl);

connection.on('SendRules', function(data:any){
    console.log(data);
});

连接一个客户端后，我从这个 Controller 调用 Send 方法:

[EnableCors("MyPolicy")]
Route("api/[controller]")]
public class MyController : Controller
{
    private readonly IMyService _myService;
    private RulesHub _rulesHub;

    public MyController(IMyService myService, IRuleService ruleService)
    {
        _myService = myService;
        _rulesHub = new RulesHub(ruleService);
    }

    [HttpPost]
    public void Post([FromBody]MyClass myClass)
    {
        _myService.Add(myClass);
        _rulesHub.Send();
    }
}

但是行 return Clients.All.InvokeAsync("SendRules", rules); 失败并显示以下异常消息:

System.NullReferenceException: 'Object reference not set to an instance of an object.'

Microsoft.AspNetCore.SignalR.Hub.Clients.get returned null.

我读到在 ASP.NET 中你应该使用像 IHubContext context = GlobalHost.ConnectionManager.GetHubContext("MyChatHub"); 这样的东西，但这不适用于这个版本。

有什么想法吗？

Answer 1

这是一个重复的问题: Call SignalR Core Hub method from Controller

您永远不应该自己创建集线器的实例。简单地将它注入(inject)您的 Controller ，例如:

[EnableCors("MyPolicy")]
Route("api/[controller]")]
public class MyController : Controller
{
    private readonly IMyService _myService;
    private  IHubContext<RulesHub> _rulesHubContext;    

    public MyController(IMyService myService, IRuleService ruleService, IHubContext<RulesHub > rulesHubContext)
    {
        _myService = myService;
        _rulesHubContext = rulesHubContext;
    }

    [HttpPost]
    public void Post([FromBody]MyClass myClass)
    {
        _myService.Add(myClass);
        // Load your rules from somewhere 
        _rulesHubContext.Clients.All.InvokeAsync("SendRules", rules);
    }
}