aws-sdk-net

You must generate an Access Key before getting started. All examples will utilize access_key_id and access_key_secret variables which represent the Access Key ID and Secret Access Key values you generated.

This example uses version 3 of the aws-sdk-net ↗ package. You must pass in the R2 configuration credentials when instantiating your S3 service client:

Client setup

In this example, you will pass credentials explicitly to the IAmazonS3 initialization. If you wish, use a shared AWS credentials file or the SDK store in-line with other AWS SDKs. Refer to Configure AWS credentials ↗ for more details.

private static IAmazonS3 s3Client;

public static void Main(string[] args)
{
  // Retrieve your S3 API credentials for your R2 bucket via API tokens (see: https://developers.cloudflare.com/r2/api/tokens)
  var accessKey = "<ACCESS_KEY_ID>";
  var secretKey = "<SECRET_ACCESS_KEY>";
  var credentials = new BasicAWSCredentials(accessKey, secretKey);
  s3Client = new AmazonS3Client(credentials, new AmazonS3Config
    {
      // Provide your Cloudflare account ID
      ServiceURL = "https://<ACCOUNT_ID>.r2.cloudflarestorage.com",
    });
}

List buckets and objects

The ListBucketsAsync ↗ and ListObjectsAsync ↗ methods can be used to list buckets under your account and the contents of those buckets respectively.

static async Task ListBuckets()
{
  var response = await s3Client.ListBucketsAsync();

  foreach (var s3Bucket in response.Buckets)
  {
    Console.WriteLine("{0}", s3Bucket.BucketName);
  }
}

sdk-example
my-bucket

static async Task ListObjectsV2()
{
  var request = new ListObjectsV2Request
  {
    BucketName = "my-bucket"
  };

  var response = await s3Client.ListObjectsV2Async(request);

  foreach (var s3Object in response.S3Objects)
  {
    Console.WriteLine("{0}", s3Object.Key);
  }
}

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Upload and retrieve objects

The PutObjectAsync ↗ and GetObjectAsync ↗ methods can be used to upload objects and download objects from an R2 bucket respectively.

Warning

DisablePayloadSigning = true and DisableDefaultChecksumValidation = true must be passed as Cloudflare R2 does not currently support the Streaming SigV4 implementation used by AWSSDK.S3.

static async Task PutObject()
{
  var request = new PutObjectRequest
  {
    FilePath = @"/path/file.txt",
    BucketName = "my-bucket",
    DisablePayloadSigning = true,
    DisableDefaultChecksumValidation = true
  };

  var response = await s3Client.PutObjectAsync(request);

  Console.WriteLine("ETag: {0}", response.ETag);
}

ETag: "186a71ee365d9686c3b98b6976e1f196"

static async Task GetObject()
{
  var bucket = "my-bucket";
  var key = "file.txt";

  var response = await s3Client.GetObjectAsync(bucket, key);

  Console.WriteLine("ETag: {0}", response.ETag);
}

ETag: "186a71ee365d9686c3b98b6976e1f196"

Generate presigned URLs

The GetPreSignedURL ↗ method allows you to sign ahead of time, giving temporary access to a specific operation. In this case, presigning a PutObject request for sdk-example/file.txt.

static string? GeneratePresignedUrl()
{
  AWSConfigsS3.UseSignatureVersion4 = true;
  var presign = new GetPreSignedUrlRequest
  {
    BucketName = "my-bucket",
    Key = "file.txt",
    Verb = HttpVerb.GET,
    Expires = DateTime.Now.AddDays(7),
  };

  var presignedUrl = s3Client.GetPreSignedURL(presign);

  Console.WriteLine(presignedUrl);

  return presignedUrl;
}

https://<ACCOUNT_ID>.r2.cloudflarestorage.com/my-bucket/file.txt?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=<credential>&X-Amz-Date=<timestamp>&X-Amz-Expires=3600&X-Amz-SignedHeaders=host&X-Amz-Signature=<signature>