public override async Task OnDisconnectedAsync(Exception exception)
{
var userId = Guid.Parse(Context.User.Identity.Name ?? string.Empty);
var channelId = Context.User.FindFirst("ChannelId").Value;
var user = await _applicationDbContext.Users.SingleOrDefaultAsync(u => u.Id == userId);
user.Connections--;
var hostConnectionId = _hostConnectionRepository.GetConnection(channelId);
if (user.Connections == 0 && hostConnectionId != null)
{
await _hostHubContext.SendUserDisconnected(hostConnectionId, userId);
_userPermissionRepository.RemoveUser(userId);
}
await _applicationDbContext.SaveChangesAsync();
await Groups.RemoveFromGroupAsync(Context.ConnectionId, channelId);
}