Exponential back off

Program.cs

private static async Task<string> DownloadStringWithRetries(string location)
{
    using (var client = new HttpClient())
    {
        var nextDelay = TimeSpan.FromSeconds(1);
        for (int i = 0; i != 3; i++)
        {
            try
            {
                Console.WriteLine("trying to download {0}.", location);
                return await client.GetStringAsync(location);
            }
            catch
            {
            }
            Console.WriteLine("trying again in {0}.", nextDelay.Seconds);
            await Task.Delay(nextDelay);
            nextDelay = nextDelay + nextDelay;
        }
        return null;
    }
}