Object Storage Service:Upload callbacks (C# SDK V1)

using System;
using System.IO;
using System.Text;
using Aliyun.OSS;
using Aliyun.OSS.Common;
using Aliyun.OSS.Util;
namespace Callback
{
    class Program
    {
        static void Main(string[] args)
        {
            Program.PutObjectCallback();
            Console.ReadKey();
        }
        public static void PutObjectCallback()
        {
            // Obtain access credentials from environment variables. Before you run this sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are set.
            var accessKeyId = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_ID");
            var accessKeySecret = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_SECRET");
            // Specify the bucket name, such as examplebucket.
            var bucketName = "examplebucket";
            // Specify the full path of the object, such as exampledir/exampleobject.txt. The full path cannot contain the bucket name.
            var objectName = "exampledir/exampleobject.txt";
           // Specify the full path of the local file, such as D:\\localpath\\examplefile.txt. If you do not specify a local path, the file is uploaded from the default path of the project.
            var localFilename = "D:\\localpath\\examplefile.txt";
            // Set the callback server URL, such as https://example.com:23450.
            const string callbackUrl = "yourCallbackServerUrl";
            // Set the value of the request body for the callback.
            const string callbackBody = "bucket=${bucket}&object=${object}&etag=${etag}&size=${size}&mimeType=${mimeType}&" +
                                        "my_var1=${x:var1}&my_var2=${x:var2}";
            //  Specify the Endpoint of the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the Endpoint to https://oss-cn-hangzhou.aliyuncs.com.
            const string endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
            // Specify the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the region to cn-hangzhou.
            const string region = "cn-hangzhou";
            // Create a ClientConfiguration instance and modify the default parameters as needed.
            var conf = new ClientConfiguration();
            // Set the signature version to V4.
            conf.SignatureVersion = SignatureVersion.V4;

            // Create an OssClient instance.
            var client = new OssClient(endpoint, accessKeyId, accessKeySecret, conf);
            client.SetRegion(region);
            try
            {
                string responseContent = "";
                var metadata = BuildCallbackMetadata(callbackUrl, callbackBody);
                using (var fs = File.Open(localFilename, FileMode.Open))
                {
                    var putObjectRequest = new PutObjectRequest(bucketName, objectName, fs, metadata);
                    var result = client.PutObject(putObjectRequest);
                    responseContent = GetCallbackResponse(result);
                }
                Console.WriteLine("Put object:{0} succeeded, callback response content:{1}", objectName, responseContent);
            }
            catch (OssException ex)
            {
                Console.WriteLine("Failed with error code: {0}; Error info: {1}. \nRequestID: {2}\tHostID: {3}",
                    ex.ErrorCode, ex.Message, ex.RequestId, ex.HostId);
            }
            catch (Exception ex)
            {
                Console.WriteLine("Failed with error info: {0}", ex.Message);
            }
        }
        // Configure the upload callback.
        private static ObjectMetadata BuildCallbackMetadata(string callbackUrl, string callbackBody)
        {
            string callbackHeaderBuilder = new CallbackHeaderBuilder(callbackUrl, callbackBody).Build();
            string CallbackVariableHeaderBuilder = new CallbackVariableHeaderBuilder().
                AddCallbackVariable("x:var1", "x:value1").AddCallbackVariable("x:var2", "x:value2").Build();
            var metadata = new ObjectMetadata();
            metadata.AddHeader(HttpHeaders.Callback, callbackHeaderBuilder);
            metadata.AddHeader(HttpHeaders.CallbackVar, CallbackVariableHeaderBuilder);
            return metadata;
        }
        // Read the message returned from the upload callback.
        private static string GetCallbackResponse(PutObjectResult putObjectResult)
        {
            string callbackResponse = null;
            using (var stream = putObjectResult.ResponseStream)
            {
                var buffer = new byte[4 * 1024];
                var bytesRead = stream.Read(buffer, 0, buffer.Length);
                callbackResponse = Encoding.Default.GetString(buffer, 0, bytesRead);
            }
            return callbackResponse;
        }
    }
}