IsAppinBackGround

private static bool IsAppInBackground(Context context)
        {
            var isInBackground = true;
            var am = (ActivityManager) context.GetSystemService(Context.ActivityService);
            if (Build.VERSION.SdkInt > BuildVersionCodes.KitkatWatch)
            {
                var runningProcesses =
                    new List<ActivityManager.RunningAppProcessInfo>(am.RunningAppProcesses);

                foreach (var processInfo in runningProcesses)
                {
                    if (processInfo.Importance == Importance.Foreground)
                    {
                        foreach (var s in processInfo.PkgList)
                        {
                            if (s.Equals(context.PackageName))
                            {
                                isInBackground = false;
                            }
                        }
                    }
                }
            }
            return isInBackground;
        }