session.On doesn't work in C# code

Hi,

I am using below code in dotnet but it seems no evt received

```dotnet
      var session = await Client.CreateSessionAsync();
       session.On(evt =>
        {
            receivedEvents.Add(evt);
            if (evt is SessionIdleEvent)
            {
                idleReceived.TrySetResult(true);
            }
        });
```