Object Storage Service:Download a file to a local disk (C# SDK V2)

Precautions

The sample code in this topic uses the China (Hangzhou) region (cn-hangzhou) as an example. By default, the public endpoint is used. If you want to access OSS from other Alibaba Cloud services in the same region, use an internal endpoint. For more information about the mappings between OSS-supported regions and endpoints, see OSS regions and endpoints.

Permissions

By default, an Alibaba Cloud account has full permissions. RAM users or RAM roles under an Alibaba Cloud account do not have any permissions by default. The Alibaba Cloud account or account administrator must grant operation permissions through RAM Policy or Bucket Policy.

Sample code

You can use the following code to download an object from a bucket to a local disk.

using OSS = AlibabaCloud.OSS.V2;  // Create an alias for the Alibaba Cloud OSS SDK to simplify subsequent use.

var region = "cn-hangzhou";  // Required. Specify the region where the bucket is located. In this example, China (Hangzhou) is used. Set the region to cn-hangzhou.
var bucket = "your bucket name";  // Required. Specify the name of the destination bucket. 
var endpoint = null as string;  // Optional. Specify the endpoint that is used to access OSS. In this example, China (Hangzhou) is used. Set the endpoint to https://oss-cn-hangzhou.aliyuncs.com.
var key = "your object name";  // Required. Specify the name of the object to be downloaded. Format: folder/objectName.
var filePath = "your file path";  // Required. Specify the path of the file to be downloaded to the local disk.

// Load the default configurations of the OSS SDK. The configurations automatically read credential information (such as AccessKey) from environment variables.
var cfg = OSS.Configuration.LoadDefault();
// Explicitly set the use of environment variables to obtain credentials for identity verification. Format: OSS_ACCESS_KEY_ID, OSS_ACCESS_KEY_SECRET.
cfg.CredentialsProvider = new OSS.Credentials.EnvironmentVariableCredentialsProvider();
// Set the region of the bucket in the configuration.
cfg.Region = region;   
// If an endpoint is specified, overwrite the default endpoint. 
if(endpoint != null)
{
    cfg.Endpoint = endpoint;
} 

// Create an OSS client instance using the configuration information.
using var client = new OSS.Client(cfg); 

// Call the GetObjectToFileAsync method to directly stream the OSS object to the local disk. This prevents large files from occupying too much memory.
var result = await client.GetObjectToFileAsync(new OSS.Models.GetObjectRequest()
{
    Bucket = bucket,
    Key = key,
}, filePath);

// Print the upload result.
Console.WriteLine("GetObjectToFile done");  // A message indicating that the operation is complete.
Console.WriteLine($"StatusCode: {result.StatusCode}");  // HTTP status code.
Console.WriteLine($"RequestId: {result.RequestId}");  // The request ID, which is used for troubleshooting in Alibaba Cloud.
Console.WriteLine("Response Headers:");  // The response header information.
result.Headers.ToList().ForEach(x => Console.WriteLine(x.Key + " : " + x.Value));  // Traverse and print all response headers.

References

For the complete sample code for downloading an object to a local disk, see GetObjectToFile.cs.