AWS SDK for .NET Documentation
ReturnValues Property
AmazonAmazon.DynamoDBv2.ModelPutItemRequestReturnValues Did this page help you?   Yes   No    Tell us about it...
Use ReturnValues if you want to get the item attributes as they appeared before they were updated with the PutItem request. For PutItem, the valid values are:

Constraints:

Allowed Values
NONE, ALL_OLD, UPDATED_OLD, ALL_NEW, UPDATED_NEW

Declaration Syntax
C#
public string ReturnValues { get; set; }

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