// Generate a new file objectPath

ObjectPath id = new ObjectPath(STORAGE_FOLDER + (new FileInfo(fullFilePath)).Name);

// Create an empty matadata list

MetadataList dataList = new MetadataList();

//Uncomment next two lines to make retention work:

//Metadata mdata1 = new Metadata("foo", string.Empty, true);

//dataList.AddMetadata(mdata1);

// Archive the file

uploadHelper.CreateObjectOnPath(id, fullFilePath, null, dataList);

// Set new retention time to the file

Metadata mdata = new Metadata("user.maui.retentionEnd", DateTime.UtcNow.AddSeconds(retentionInSeconds), false);

MetadataList dataList2 = new MetadataList();

dataList2.AddMetadata(mdata);

this.restApi.SetUserMetadata(id, dataList2);