Perform a multipart copy of an Amazon S3 object using an AWS SDK

    using System;
    using System.Collections.Generic;
    using System.Threading.Tasks;
    using Amazon.S3;
    using Amazon.S3.Model;

    /// <summary>
    /// This example shows how to perform a multi-part copy from one Amazon
    /// Simple Storage Service (Amazon S3) bucket to another.
    /// </summary>
    public class MPUapiCopyObj
    {
        private const string SourceBucket = "amzn-s3-demo-bucket1";
        private const string TargetBucket = "amzn-s3-demo-bucket2";
        private const string SourceObjectKey = "example.mov";
        private const string TargetObjectKey = "copied_video_file.mov";

        /// <summary>
        /// This method starts the multi-part upload.
        /// </summary>
        public static async Task Main()
        {
            var s3Client = new AmazonS3Client();
            Console.WriteLine("Copying object...");
            await MPUCopyObjectAsync(s3Client);
        }

        /// <summary>
        /// This method uses the passed client object to perform a multipart
        /// copy operation.
        /// </summary>
        /// <param name="client">An Amazon S3 client object that will be used
        /// to perform the copy.</param>
        public static async Task MPUCopyObjectAsync(AmazonS3Client client)
        {
            // Create a list to store the copy part responses.
            var copyResponses = new List<CopyPartResponse>();

            // Setup information required to initiate the multipart upload.
            var initiateRequest = new InitiateMultipartUploadRequest
            {
                BucketName = TargetBucket,
                Key = TargetObjectKey,
            };

            // Initiate the upload.
            InitiateMultipartUploadResponse initResponse =
                await client.InitiateMultipartUploadAsync(initiateRequest);

            // Save the upload ID.
            string uploadId = initResponse.UploadId;

            try
            {
                // Get the size of the object.
                var metadataRequest = new GetObjectMetadataRequest
                {
                    BucketName = SourceBucket,
                    Key = SourceObjectKey,
                };

                GetObjectMetadataResponse metadataResponse =
                    await client.GetObjectMetadataAsync(metadataRequest);
                var objectSize = metadataResponse.ContentLength; // Length in bytes.

                // Copy the parts.
                var partSize = 5 * (long)Math.Pow(2, 20); // Part size is 5 MB.

                long bytePosition = 0;
                for (int i = 1; bytePosition < objectSize; i++)
                {
                    var copyRequest = new CopyPartRequest
                    {
                        DestinationBucket = TargetBucket,
                        DestinationKey = TargetObjectKey,
                        SourceBucket = SourceBucket,
                        SourceKey = SourceObjectKey,
                        UploadId = uploadId,
                        FirstByte = bytePosition,
                        LastByte = bytePosition + partSize - 1 >= objectSize ? objectSize - 1 : bytePosition + partSize - 1,
                        PartNumber = i,
                    };

                    copyResponses.Add(await client.CopyPartAsync(copyRequest));

                    bytePosition += partSize;
                }

                // Set up to complete the copy.
                var completeRequest = new CompleteMultipartUploadRequest
                {
                    BucketName = TargetBucket,
                    Key = TargetObjectKey,
                    UploadId = initResponse.UploadId,
                };
                completeRequest.AddPartETags(copyResponses);

                // Complete the copy.
                CompleteMultipartUploadResponse completeUploadResponse =
                    await client.CompleteMultipartUploadAsync(completeRequest);
            }
            catch (AmazonS3Exception e)
            {
                Console.WriteLine($"Error encountered on server. Message:'{e.Message}' when writing an object");
            }
            catch (Exception e)
            {
                Console.WriteLine($"Unknown encountered on server. Message:'{e.Message}' when writing an object");
            }
        }
    }