با متد زیر

public static bool CheckNetworkConnection()
        {
            var connectivityManager = (ConnectivityManager)Application.Context.GetSystemService(Context.ConnectivityService);
            var activeNetworkInfo = connectivityManager.ActiveNetworkInfo;
            if (activeNetworkInfo != null && activeNetworkInfo.IsConnectedOrConnecting)
            {
                return true;
            }
            else
            {
                return false;
            }
        }