AWS SDK for .NET Documentation
Metadata Property
AmazonAmazon.S3.UtilS3PostUploadRequestMetadata Did this page help you?   Yes   No    Tell us about it...
Metadata to set on the uploaded object
Declaration Syntax
C#
public IDictionary<string, string> Metadata { get; set; }
Remarks
If keys do not begin with 'x-amz-meta-' it will be added at POST time.

Assembly: AWSSDK (Module: AWSSDK) Version: 1.5.60.0 (1.5.60.0)