C#

public abstract class ObjectCollection<T> : Dictionary<int,T>, IDisposable where T : ISomeInterface

private bool disposedValue = false; // To detect redundant calls

protected virtual void Dispose(bool disposing)
{
    if (!disposedValue)
    {
        if (disposing)
        {
            // TODO: dispose managed state (managed objects).
        }

        // TODO: free unmanaged resources (unmanaged objects) and override a finalizer below.
        // TODO: set large fields to null.

        disposedValue = true;
    }
}

// TODO: override a finalizer only if Dispose(bool disposing) above has code to free unmanaged resources.
// ~CustomField() {
//   // Do not change this code. Put cleanup code in Dispose(bool disposing) above.
//   Dispose(false);
// }

// This code added to correctly implement the disposable pattern.
public void Dispose()
{
    // Do not change this code. Put cleanup code in Dispose(bool disposing) above.
    Dispose(true);
    // TODO: uncomment the following line if the finalizer is overridden above.
    // GC.SuppressFinalize(this);
}

Sascha Lefèvre wrote:

You just need to re-order to make IDisposable apply to the class instead of T

public abstract class ObjectCollection<T> : Dictionary<int,T>, IDisposable
    where T : ISomeInterface
{
   // ...
}

Bernhard Hiller wrote:

But does it really reconnect automatically?

1. When the client first connects, it sends a unique value that helps identification (since SignalR connectionIds are not persistent).
2. This is saved in dictionary with value as true (for connected).
3. When the client is disconnected, the value is set to false.
4. When the notification is sent from server to client, we check if there is any client with value as false in the dictionary. If yes, we save the client identifiers.
5. Next time they connect, the notification is sent again.

1. Drone notes all the dogs available.
2. If any dogs runs away to eat grass or whatever, it makes note of that too.
3. If a wolf is noticed, all dogs are notified. Drone also knows one dog is not there and will need to notify this dog later.
4. As soon as dog is back, it is send message.
5. If any new dog joins in, that too gets the message.

Bernhard Hiller wrote:

We have to take care of a flock of sheep. A shepherding drone is hovering over the area and searching for wolves. After detection of a wolf, it will notify the dogs and tell them where the wolves are etc. In most case there is one drone and one dog, but sometimes there may be many. With some trees around, the connection between the drone and the network may get disrupted.

An alternative solution is the dogs querying the drone's LastWolfDetected property in short intervals. Or the drones sending the LastWolfDetected message to a server, and the dogs query the server.
Anyway, the dogs must be informed reliably.