public static RetryPolicy RetryExponential(int retryCount, TimeSpan minBackoff, TimeSpan maxBackoff, TimeSpan deltaBackoff)
{
      // Do any argument Pre-validation here, i.e. enforce max retry count etc.
      return () =>
      {
            return (int currentRetryCount, Exception lastException, out TimeSpan retryInterval) =>
            {
                 if (currentRetryCount < retryCount)
                 {
                      Random r = new Random();

                      // Calculate Exponential backoff with +/- 20% tolerance
                      int increment = (int)((Math.Pow(2, currentRetryCount) - 1) * r.Next((int)(deltaBackoff.TotalMilliseconds * 0.8), (int)(deltaBackoff.TotalMilliseconds * 1.2)));

                      // Enforce backoff boundaries
                      int timeToSleepMsec = (int)Math.Min(minBackoff.TotalMilliseconds + increment, maxBackoff.TotalMilliseconds);

                      retryInterval = TimeSpan.FromMilliseconds(timeToSleepMsec);

                      return true;
                 }

                 retryInterval = TimeSpan.Zero;
                 return false;
            };
      };
}