test.cs

using System;
using System.IO;
using System.Text;

using Amazon;
using Amazon.S3;
using Amazon.S3.Model;

namespace AWSUploadTest
{
    class Program
    {
        public static void Main(string[] args)
        {
            // basic params
            string accessKey = "mykey";
            string secretAccessKey = "mysecret";
            string bucketName = "mybucket";
            string keyName = "test.txt";
            string sourceFileName = @"c:\temp\upload.txt";

            // initialize our client
            AmazonS3 client = Amazon.AWSClientFactory.CreateAmazonS3Client(accessKey, secretAccessKey);

            // initialize our request
            PutObjectRequest request = new PutObjectRequest();

            // we'll use a stream so we can efficiently handle files large or small
            FileStream fs = new FileStream(sourceFileName, FileMode.Open);
            
            // setup the request
            request.WithInputStream(fs);
            request.WithBucketName(bucketName);
            request.WithKey(keyName);

            // do it!
            client.PutObject(request);

            // fin!
            fs.Close();
        }
    }
}