title: Connection ID when calling SignalR Core Hub method from Controller
body: <p>This is a follow-up to <a href="https://stackoverflow.com/q/46904678">another question and answer</a>.  What's the effect of calling <code>HubContext.Clients.Caller</code> or <code>HubContext.Clients.Others</code> from the controller?  I see it depends on the <a href="https://github.com/aspnet/SignalR/blob/e39d453a8238c222f400fd081060c6b506291275/src/Microsoft.AspNetCore.SignalR.Core/HubCallerClients.cs#L10" rel="noreferrer">connection ID</a>.  What value would it have in this situation?</p>
  
  <p>If the connection ID (and thus <code>Caller</code> and <code>Others</code>) is invalid then (from within the controller action) how could I obtain a connection ID (for the client currently calling the Web API) that I could use with <code>HubContext.Clients</code>'s methods?</p>