Question

我刚开始使用SignalR，并且能够毫无问题地向所有连接的客户端广播消息。我现在想让我的客户端（javascript）加入一个组，只接收该组的消息。在我的集线器中，我有以下方法添加到命名组的连接：

    public Task JoinGroup(string groupName)
    {
        return this.Groups.Add(Context.ConnectionId, groupName);
    }

在客户端上，我有以下JS：

        var latLonBounds = new google.maps.LatLngBounds();
        var tripIdentifier = '@Model.TripIdentifier';
        $(function () {
            var hub = $.connection.locationHub;
            hub.client.updateLocation = function (coordinates) {
                  // Implementation omitted
                });

                latLonBounds.extend(position);
                map.fitBounds(latLonBounds);
            };
            $.connection.hub.logging = true;
            $.connection.hub.start().done(function() {
                hub.server.joinGroup(tripIdentifier);
            });
        });

加载我的网页后，在Chrome中，我在控制台中看到了以下网址的HTTP 500：

http://localhost:49914/signalr/send?transport=serverSentEvents&connectionToken=AQAAANCMnd8BFdERjHoAwE%2FCl%2BsBAAAA8OmZGDrRfEaOjaHahkkarwAAAAACAAAAAAAQZgAAAAEAACAAAADM78kCBInmZa7OROdPoXraiugBXLR5Xu3htxYC2JSnSAAAAAAOgAAAAAIAACAAAAAZwnPx6GMKOiw%2FivqQPlSfCb4WNP342YxvGyBpalmjSDAAAADljl1vg%2F7GYtD3R4AA2A9LXEnNZkyQVQjDUrW7ZVbvfPpWz1GCcOn6aw5yrkrWFrhAAAAAyX5otz0Xhx8tuIRgX2Pr1b9ZWFMvoairvqzns1%2FhjN%2BRhDIuAqAfonTbsZDjkdyDAZXzAKQqwTEKhpa5LYBhKg%3D%3D

在Visual Studio中，我看到以下堆栈跟踪：

SignalR exception thrown by Task: System.AggregateException: One or more errors occurred. ---> System.MissingMethodException: No parameterless constructor defined for this object.
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Activator.CreateInstance(Type type)
   at Microsoft.AspNet.SignalR.Hubs.DefaultHubActivator.Create(HubDescriptor descriptor)
   at Microsoft.AspNet.SignalR.Hubs.DefaultHubManager.ResolveHub(String hubName)
   at Microsoft.AspNet.SignalR.Hubs.HubDispatcher.CreateHub(IRequest request, HubDescriptor descriptor, String connectionId, StateChangeTracker tracker, Boolean throwIfFailedToCreate)
   at Microsoft.AspNet.SignalR.Hubs.HubDispatcher.OnReceived(IRequest request, String connectionId, String data)
   at Microsoft.AspNet.SignalR.PersistentConnection.<>c__DisplayClassa.<>c__DisplayClassc.<ProcessRequest>b__7()
   at Microsoft.AspNet.SignalR.TaskAsyncHelper.FromMethod(Func`1 func)
   --- End of inner exception stack trace ---
---> (Inner Exception #0) System.MissingMethodException: No parameterless constructor defined for this object.
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Activator.CreateInstance(Type type)
   at Microsoft.AspNet.SignalR.Hubs.DefaultHubActivator.Create(HubDescriptor descriptor)
   at Microsoft.AspNet.SignalR.Hubs.DefaultHubManager.ResolveHub(String hubName)
   at Microsoft.AspNet.SignalR.Hubs.HubDispatcher.CreateHub(IRequest request, HubDescriptor descriptor, String connectionId, StateChangeTracker tracker, Boolean throwIfFailedToCreate)
   at Microsoft.AspNet.SignalR.Hubs.HubDispatcher.OnReceived(IRequest request, String connectionId, String data)
   at Microsoft.AspNet.SignalR.PersistentConnection.<>c__DisplayClassa.<>c__DisplayClassc.<ProcessRequest>b__7()
   at Microsoft.AspNet.SignalR.TaskAsyncHelper.FromMethod(Func`1 func)<---

如果我从我的JS中删除了对hub.server.joinGroup(tripIdentifier);的调用，那么我就不会得到HTTP 500 /异常，所以看起来这行是异常的来源。

对于我可以做些什么来进行团体注册工作的任何建议都将不胜感激。

谢谢！

Answer 1

这是堆栈中告诉你错误的部分：

---> (Inner Exception #0) System.MissingMethodException: No parameterless constructor defined    for this object.
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Activator.CreateInstance(Type type)
   at Microsoft.AspNet.SignalR.Hubs.DefaultHubActivator.Create(HubDescriptor descriptor

基本上说的是你的hub类没有无参数构造函数。如果您尝试为集线器设置依赖项注入，则表明您在使用SignalR注册依赖项解析器时遇到问题。如果您提供更多详细信息，我们可以帮助您解决问题。

从客户端调用服务器方法时SignalR HTTP 500

1 个答案: