title: SignalR - Update specific user (Push notifications)
body: <p>I'm having troubles to update only one specific user.</p>
  
  <p>I'm working on some asp.net core web application and I want to implement push notification to my project. I'll explain a little more about what am i doing in my application.</p>
  
  <p>I have a page where users can post something (like on facebook). On that post everyone can like/unlike it (like button) or comment it (can delete comments too). And my implementation of signalR on that part is working perfectly with <code>await Clients.All.SendAsync("UpdateComments", userId, postId);</code>. </p>
  
  <p>Now i want to send notification to the user whose post is.
  I tries to do that on this way <code>await Clients.User(userId).SendAsync("SendNotification", notificationText);</code> but not working. When i debuged it, on this part <code>User(someId)</code> it expect me to send <code>connectionId</code> which i don't have for user which i want to update. I have connectionId only for user who invoked current connection.</p>
  
  <p><strong>My question is:</strong> How can i update user with userId from my table or how can i get connectionId based on my userId? <strong>OR</strong> If i can't on any way to accomplish this, is there a way that i can automatically add user (when he log in to application) in some signalR group connection whithout need for user to activate connection by himself? </p>
  
  <p>I googled a lot, but i didn't found answer. 
  <a href="https://docs.microsoft.com/en-us/aspnet/core/tutorials/signalr?tabs=visual-studio&amp;view=aspnetcore-3.1" rel="nofollow noreferrer">This</a> is link which i followed to implement signalR in my app.</p>