//Client Code

​

Dictionary<string, string> queryString = new Dictionary<string, string>();

        queryString.Add("key1", "value1");

        queryString.Add("key2", "value2");

        hubConnection = new HubConnection("http://localhost:49493/signalr/hubs", queryString);

//In hub

public override Task OnConnected()

{

 var value1 = Convert.ToString(Context.QueryString["key1"]);

 var value2 = Convert.ToString(Context.QueryString["key2"]);

 return base.OnConnected();

}