[英]How to send a message to all clients on SignalR alpha for NET Core 2.0
我正在使用signalR 1.0.0-alpha2-final,并希望向所有连接的客户端发送消息。
我已经以本教程为起点。
我有从Hub继承的RulesHub:
[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,我有以下代码可以连接到集线器:
let connection = new signalR.HubConnection(rulesMonitorUrl);
connection.on('SendRules', function(data:any){
console.log(data);
});
连接一个客户端后,我从此控制器调用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();
}
}
但是该行return Clients.All.InvokeAsync("SendRules", rules);
失败,并显示以下异常消息:
System.NullReferenceException:'对象引用未设置为对象的实例。
Microsoft.AspNetCore.SignalR.Hub.Clients.get返回null。
我已经读过,在ASP.NET中,您应该使用IHubContext context = GlobalHost.ConnectionManager.GetHubContext("MyChatHub");
但这不适用于该版本。
有任何想法吗?
这是一个重复的问题: 从Controller调用SignalR Core Hub方法
您永远不要自己创建一个中心实例。 简单地将其注入到控制器中,如下所示:
[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);
}
}
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