List all files with filename under an Amazon S3 folder using ListObjects feature. No special permissions needed, just to save cost.

AmazonS3Demo.cs

using Amazon.S3;
using System;

class Program
{
    static void Main(string[] args)
    {
        var bucketName = "my-bucket";
        string accessKeyId = "my-access-key-id";
        string secretAccessKey = "secret-access-key-id";

        var s3Client = new AmazonS3Client(accessKeyId, secretAccessKey);

        var totalDirs = 0;
        var totalFile = 0;
        var totalSize = 0L;

        var objects = s3Client.ListObjects(bucketName);

        foreach (var item in objects.S3Objects)
        {
            var key = item.Key;
            totalSize += item.Size;

            if (key.EndsWith("/"))
            {
                totalDirs++;
                continue;
            }
            else totalFile++;

            Console.WriteLine(key);
        }

        Console.WriteLine();
        Console.WriteLine("Total Objects : {0}", objects.S3Objects.Count);
        Console.WriteLine("Total Files   : {0}", totalFile);
        Console.WriteLine("Total Folders : {0}", totalDirs);
        Console.WriteLine("Total Size    : {0:N0} bytes", totalSize);

        Console.ReadLine();
    }
}