Object Storage Service:Append upload by using OSS SDK for .NET

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 use append upload, you must have the oss:PutObject permission. For more information, see Attach a custom policy to a RAM user.

• If the object to which you want to append content does not exist, an appendable object is created when you call the AppendObject operation.

• If the object to which you want to append content exists:

  • If the object is an appendable object and the specified position from which the append operation starts is equal to the current object size, the data is appended to the end of the object.

  • If the object is an appendable object and the specified position from which the append operation starts is not equal to the current object size, the PositionNotEqualToLength error is returned.

  • If the object is not an appendable object, the ObjectNotAppendable error is returned.

Examples

The following sample code provides an example on how to upload an object by using append upload:

using Aliyun.OSS;

// Specify the endpoint of the region in which the bucket is located. For example, if the bucket is located 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 name of the bucket. Example: examplebucket. 
var bucketName = "examplebucket";
// Specify the full path of the object. Do not include the bucket name in the full path. Example: exampledir/exampleobject.txt. 
var objectName = "exampledir/exampleobject.txt";
// Specify the full path of the local file. Example: D:\\localpath\\examplefile.txt. By default, if you do not specify the path of the local file, the file is uploaded from the path of the project to which the sample program belongs. 
var localFilename = "D:\\localpath\\examplefile.txt";
// Create an OSSClient instance. 
var client = new OssClient(endpoint, accessKeyId, accessKeySecret);
// The position for the first append upload is 0, and the position for the next append upload is included in the response. The position from which the next append operation starts is the current length of the object. 
long position = 0;
try
{
    var metadata = client.GetObjectMetadata(bucketName, objectName);
    position = metadata.ContentLength;
}
catch (Exception) { }
try
{
    using (var fs = File.Open(localFilename, FileMode.Open))
    {
        var request = new AppendObjectRequest(bucketName, objectName)
        {
            ObjectMetadata = new ObjectMetadata(),
            Content = fs,
            Position = position
        };
        // Perform the append operation. 
        var result = client.AppendObject(request);
        // Specify the position from which the append operation starts. 
        position = result.NextAppendPosition;
        Console.WriteLine("Append object succeeded, next append position:{0}", position);
    }
    // Query the position from which the next append operation starts and perform the second append operation. 
    using (var fs = File.Open(localFilename, FileMode.Open))
    {
        var request = new AppendObjectRequest(bucketName, objectName)
        {
            ObjectMetadata = new ObjectMetadata(),
            Content = fs,
            Position = position
        };
        var result = client.AppendObject(request);
        position = result.NextAppendPosition;
        Console.WriteLine("Append object succeeded, next append position:{0}", position);
    }
}
catch (Exception ex)
{
    Console.WriteLine("Append object failed, {0}", ex.Message);
}

References

• For more information about the complete sample code that is used to perform append upload, visit GitHub.

• For more information about the API operation that you can call to perform append upload, see AppendObject.