Overview

This document provides an overview of APIs and SDK code samples related to object downloads.

API	Operation	Description
GET Object	Downloading an object	Downloads an object to the local file system.

SDK API References

For the parameters and method description of all the APIs in the SDK, see API Documentation.

Advanced APIs (Recommended)

Downloading an object (checkpoint restart)

The advanced version of the GET Object API uses more encapsulated logic to allow you to suspend, resume (via checkpoint restart), or cancel download requests.

Note：

If your .NET Framework version is 4.0 or earlier, advanced APIs are not available. For more information, please see Backward Compatibility.

Sample 1: downloading an object

using COSXML.Model.Object;
using COSXML.Auth;
using COSXML.Transfer;
using System;
using COSXML;
namespace COSSnippet
{
  public class TransferDownloadObjectModel {
     private CosXml cosXml;
     TransferDownloadObjectModel() {
      CosXmlConfig config = new CosXmlConfig.Builder()
        .SetRegion("COS_REGION") // Set the default region. For abbreviations of COS regions, visit https://intl.cloud.tencent.com/document/product/436/6224?from_cn_redirect=1.
        .Build();

      string secretId = "SECRET_ID";   // SecretId of the TencentCloud API. For more information about how to obtain the API key, see https://console.cloud.tencent.com/cam/capi.
      string secretKey = "SECRET_KEY"; // SecretKey of the TencentCloud API. For more information about how to obtain the API key, see https://console.cloud.tencent.com/cam/capi.
      long durationSecond = 600;          // Validity period of the request signature in seconds
      QCloudCredentialProvider qCloudCredentialProvider = new DefaultQCloudCredentialProvider(secretId, 
        secretKey, durationSecond);

      this.cosXml = new CosXmlServer(config, qCloudCredentialProvider);
    }
     /// Download an object via advanced API
    public async void TransferDownloadObject()
    {
      // Initialize TransferConfig
      TransferConfig transferConfig = new TransferConfig();

      // Initialize TransferManager
      TransferManager transferManager = new TransferManager(cosXml, transferConfig);

      String bucket = "examplebucket-1250000000"; // Bucket name in the format of BucketName-APPID
      String cosPath = "exampleobject"; // Location identifier of the object in the bucket, i.e., the object key
      string localDir = System.IO.Path.GetTempPath();// Local file directory
      string localFileName = "my-local-temp-file"; // Filename of the local file

      // Download an object
      COSXMLDownloadTask downloadTask = new COSXMLDownloadTask(bucket, cosPath, 
        localDir, localFileName);

      downloadTask.progressCallback = delegate (long completed, long total)
      {
          Console.WriteLine(String.Format("progress = {0:##.##}%", completed * 100.0 / total));
      };
       try {
        COSXML.Transfer.COSXMLDownloadTask.DownloadTaskResult result = await 
          transferManager.DownloadAsync(downloadTask);
        Console.WriteLine(result.GetResultInfo());
        string eTag = result.eTag;
      }
      catch (COSXML.CosException.CosClientException clientEx)
      {
        // Request failed
        Console.WriteLine("CosClientException: " + clientEx);
      }
      catch (COSXML.CosException.CosServerException serverEx)
      {
        // Request failed
        Console.WriteLine("CosServerException: " + serverEx.GetInfo());
      }
    }
      static void Main(string[] args)
    {
      TransferDownloadObjectModel m = new TransferDownloadObjectModel();
       /// Download an object via advanced API
      m.TransferDownloadObject();
    }
  }
}

Note：

For the complete sample, go to GitHub.

Sample 2: setting checkpoint restart for download

COSXMLDownloadTask downloadTask = new COSXMLDownloadTask(request);
// Enable checkpoint restart. If an object is not completely downloaded, the download will be started from the checkpoint.
// If the local file contains content that does not meet the requirements of the current download, the download may fail. You can delete the file and try again.
downloadTask.SetResumableDownload(true);
try {
 COSXML.Transfer.COSXMLDownloadTask.DownloadTaskResult result = await 
 transferManager.DownloadAsync(downloadTask);
 Console.WriteLine(result.GetResultInfo());
 string eTag = result.eTag;
} catch (Exception e) {
 Console.WriteLine("CosException: " + e);
}

Note：

For the complete sample, go to GitHub.

Sample 3: batch download

TransferConfig transferConfig = new TransferConfig();
// Initialize TransferManager
TransferManager transferManager = new TransferManager(cosXml, transferConfig);
// Bucket name in the format of `BucketName-APPID`. You can get APPID by referring to https://console.cloud.tencent.com/developer.
string bucket = "examplebucket-1250000000";
string localDir = System.IO.Path.GetTempPath();// Local file directory
for (int i = 0; i < 5; i++) {
// Download an object
string cosPath = "exampleobject" + i; // Location identifier of an object in the bucket, i.e. the object key
string localFileName = "my-local-temp-file"; // Filename of the local file
COSXMLDownloadTask downloadTask = new COSXMLDownloadTask(bucket, cosPath, 
  localDir, localFileName);
await transferManager.DownloadAsync(downloadTask);
}

Note：

For the complete sample, go to GitHub.

Sample 4: limiting single-URL download speed

TransferConfig transferConfig = new TransferConfig();
// Initialize TransferManager
TransferManager transferManager = new TransferManager(cosXml, transferConfig);
String bucket = "examplebucket-1250000000"; // Bucket name in the format of BucketName-APPID
String cosPath = "exampleobject"; // Location identifier of the object in the bucket, i.e., the object key
string localDir = System.IO.Path.GetTempPath();// Local file directory
string localFileName = "my-local-temp-file"; // Filename of the local file

GetObjectRequest request = new GetObjectRequest(bucket, 
       cosPath, localDir, localFileName);
request.LimitTraffic(8 * 1000 * 1024); // Limit the speed to 1 MB/s.
COSXMLDownloadTask downloadTask = new COSXMLDownloadTask(request);
await transferManager.DownloadAsync(downloadTask);

Note：

For the complete sample, go to GitHub.

Simple Operations

Downloading an object

Description

This API is used to download an object to the local file system.

Sample 1: simple download of a single object

using COSXML.Model.Object;
using COSXML.Auth;
using System;
using COSXML;
namespace COSSnippet
{
  public class GetObjectModel {
     private CosXml cosXml;
     GetObjectModel() {
      CosXmlConfig config = new CosXmlConfig.Builder()
        .SetRegion("COS_REGION") // Set the default region. For abbreviations of COS regions, visit https://intl.cloud.tencent.com/document/product/436/6224?from_cn_redirect=1. 
        .Build();

      string secretId = "SECRET_ID";   // SecretId of the TencentCloud API. For more information about how to obtain the API key, see https://console.cloud.tencent.com/cam/capi.
      string secretKey = "SECRET_KEY"; // SecretKey of the TencentCloud API. For more information about how to obtain the API key, see https://console.cloud.tencent.com/cam/capi.
      long durationSecond = 600;          // Validity period of the request signature in seconds
      QCloudCredentialProvider qCloudCredentialProvider = new DefaultQCloudCredentialProvider(secretId, 
        secretKey, durationSecond);

      this.cosXml = new CosXmlServer(config, qCloudCredentialProvider);
    }
     /// Download an object
    public void GetObject()
    {
      //.cssg-snippet-body-start:[get-object]
      try
      {
        // Bucket name in the format of `BucketName-APPID`. You can get APPID by referring to https://console.cloud.tencent.com/developer.
        string bucket = "examplebucket-1250000000";
        string key = "exampleobject"; // Object key
        string localDir = System.IO.Path.GetTempPath();// Local file directory
        string localFileName = "my-local-temp-file"; // Filename of the local file
        GetObjectRequest request = new GetObjectRequest(bucket, key, localDir, localFileName);
        // Set the progress callback
        request.SetCosProgressCallback(delegate (long completed, long total)
        {
          Console.WriteLine(String.Format("progress = {0:##.##}%", completed * 100.0 / total));
        });
        // Execute the request
        GetObjectResult result = cosXml.GetObject(request);
        // Request succeeded
        Console.WriteLine(result.GetResultInfo());
      }
      catch (COSXML.CosException.CosClientException clientEx)
      {
        // Request failed
        Console.WriteLine("CosClientException: " + clientEx);
      }
      catch (COSXML.CosException.CosServerException serverEx)
      {
        // Request failed
        Console.WriteLine("CosServerException: " + serverEx.GetInfo());
      }
    }
     static void Main(string[] args)
    {
      GetObjectModel m = new GetObjectModel();
      /// Download an object
      m.GetObject();
    }
  }
}

Note：

For the complete sample, go to GitHub.

Sample 2: downloading an object to memory

using COSXML.Model.Object;
using COSXML.Auth;
using System;
using COSXML;
namespace COSSnippet
{
  public class GetObjectModel {
     private CosXml cosXml;
     GetObjectModel() {
      CosXmlConfig config = new CosXmlConfig.Builder()
        .SetRegion("COS_REGION") // Set the default region. For abbreviations of COS regions, visit https://intl.cloud.tencent.com/document/product/436/6224?from_cn_redirect=1. 
        .Build();

      string secretId = "SECRET_ID";   // SecretId of the TencentCloud API. For more information about how to obtain the API key, see https://console.cloud.tencent.com/cam/capi.
      string secretKey = "SECRET_KEY"; // SecretKey of the TencentCloud API. For more information about how to obtain the API key, see https://console.cloud.tencent.com/cam/capi.
      long durationSecond = 600;          // Validity period of the request signature in seconds
      QCloudCredentialProvider qCloudCredentialProvider = new DefaultQCloudCredentialProvider(secretId, 
        secretKey, durationSecond);

      this.cosXml = new CosXmlServer(config, qCloudCredentialProvider);
    }
     /// Download the returned bytes data
    public void downloadToMem() {
      try
      {
        // Bucket name in the format of `BucketName-APPID`. You can get APPID by referring to https://console.cloud.tencent.com/developer.
        string bucket = "examplebucket-1250000000";
        string key = "exampleobject"; // Object key

        GetObjectBytesRequest request = new GetObjectBytesRequest(bucket, key);
        // Set the progress callback
        request.SetCosProgressCallback(delegate (long completed, long total)
        {
          Console.WriteLine(String.Format("progress = {0:##.##}%", completed * 100.0 / total));
        });
        // Execute the request
        GetObjectBytesResult result = cosXml.GetObject(request);
        // Get content for the byte array
        byte[] content = result.content;
        // Request succeeded
        Console.WriteLine(result.GetResultInfo());
      }
      catch (COSXML.CosException.CosClientException clientEx)
      {
        // Request failed
        Console.WriteLine("CosClientException: " + clientEx);
      }
      catch (COSXML.CosException.CosServerException serverEx)
      {
        // Request failed
        Console.WriteLine("CosServerException: " + serverEx.GetInfo());
      }
    }
     // .cssg-methods-pragma
     static void Main(string[] args)
    {
      GetObjectModel m = new GetObjectModel();
       /// Download the object to memory
      m.downloadToMem();
      // .cssg-methods-pragma
    }
  }
}

Note：

For the complete sample, go to GitHub.