Object Storage Service:Check whether a file exists (C# SDK V1)

Usage notes

• In this topic, the public endpoint of the China (Hangzhou) region is used. If you want to access OSS from other Alibaba Cloud services in the same region as OSS, use an internal endpoint. For more information about OSS regions and endpoints, see Regions and endpoints.

• In this topic, an OSSClient instance is created by using an OSS endpoint. If you want to create an OSSClient instance by using custom domain names or Security Token Service (STS), see Initialization.

• To determine whether an object exists, you must have the oss:GetObject permission. For more information, see Attach a custom policy to a RAM user.

Sample code

The following code provides an example on how to determine whether an object exists in a bucket:

using Aliyun.OSS;
using Aliyun.OSS.Common;
// Replace yourEndpoint with 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.
var endpoint = "yourEndpoint";
// Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured.
var accessKeyId = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_ID");
var accessKeySecret = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_SECRET");
// Specify the bucket name. Example: examplebucket.
var bucketName = "examplebucket";
// Specify the full path of the object. The full path cannot contain the bucket name. Example: exampledir/exampleobject.txt.
var objectName = "exampledir/exampleobject.txt";
// 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();

// Use Signature V4.
conf.SignatureVersion = SignatureVersion.V4;

// Create an OssClient instance.
var client = new OssClient(endpoint, accessKeyId, accessKeySecret, conf);
try
{
    // Check whether the file exists.
    var exist = client.DoesObjectExist(bucketName, objectName);
    Console.WriteLine("Object exist ? " + exist);
}
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);
}

References

For the complete sample code that is used to determine whether an object exists, visit GitHub.