AWS SDK for .NET Documentation
ContentType Property
AmazonAmazon.S3.UtilS3PostUploadRequestContentType Did this page help you?   Yes   No    Tell us about it...
Content type for the uploaded data
Declaration Syntax
C#
public string ContentType { get; set; }
Remarks
If this is not set, an attempt will be made to infer it from the extension on Key or Path (in that order), otherwise 'application/octet-stream' will be assumed.

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