AWS SDK for .NET Documentation
ConditionalOperator Property
AmazonAmazon.DynamoDBv2.ModelUpdateItemRequestConditionalOperator Did this page help you?   Yes   No    Tell us about it...
A logical operator to apply to the conditions in the Expected map: If you omit ConditionalOperator, then AND is used as the default. The operation will succeed only if the entire map evaluates to true.

Constraints:

Allowed Values
AND, OR

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

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