Blazor WebAssembly SignalR send to specific user problem with context

I'm trying to send a message to a specific client in my Blazor WebAssembly project.

Startup.cs

services.AddSignalR();
....

app.UseEndpoints(endpoints =>
            {
                endpoints.MapRazorPages();
                endpoints.MapControllers();
                endpoints.MapHub<OrderHub>("/orderhub");
                endpoints.MapFallbackToFile("index.html");
            });

Client Code

protected override async Task OnInitializedAsync()
 {
    hubConnection = new HubConnectionBuilder()
           .WithUrl(NavigationManager.ToAbsoluteUri("/orderhub"))
           .Build();
            await hubConnection.StartAsync();
            await hubConnection.SendAsync("SendItemsCountMessage", orderpositions.Sum(x => x.amount));
 }

Hub.cs

public class OrderHub : Hub
{
    public async Task SendItemsCountMessage(int ItemsCount)
    {
        await Clients.All.SendAsync("ReceiveItemMessage", ItemsCount);
    }
}

Now I want to change it to have the option to send to a specific user:

public async Task SendItemsCountMessage(int ItemsCount)
{
            string conID = Context.ConnectionId;
            await Clients.User(conID).SendAsync("ReceiveItemMessage", ItemsCount);
}

But the context is null, with a user or without, with a logged in user or unauthorized, it all doesn't seems to matter. Any idea how to get the right Context.ConnectionId, best without being logged in user?

Maybe I need something like this?

Is it possible that I have to use bearer token authentication in my application and then send a generated token to Hub.cs where with var context = HttpContext.Request.Query[Token] I can get my Context?