An attribute value used with conditional DeleteItem , PutItem or UpdateItem operations. Amazon DynamoDB will check to see if the attribute value already exists; or if the attribute exists and has a particular value before updating it.

Inheritance Hierarchy

System.Object
Amazon.DynamoDBv2.Model.ExpectedAttributeValue

Namespace: Amazon.DynamoDBv2.Model
Assembly: AWSSDK.dll
Version: 2.0.0.3

Syntax

public class ExpectedAttributeValue : Object

The ExpectedAttributeValue type exposes the following members

Constructors

	Name	Description
	ExpectedAttributeValue()

Properties

	Name	Description
	Exists	Causes Amazon DynamoDB to evaluate the value before attempting a conditional operation: If Exists is true, Amazon DynamoDB will check to see if that attribute value already exists in the table. If it is found, then the operation succeeds. If it is not found, the operation fails with a ConditionalCheckFailedException. If Exists is false, Amazon DynamoDB assumes that the attribute value does not exist in the table. If in fact the value does not exist, then the assumption is valid and the operation succeeds. If the value is found, despite the assumption that it does not exist, the operation fails with a ConditionalCheckFailedException. The default setting for Exists is true. If you supply a Value all by itself, Amazon DynamoDB assumes the attribute exists: You don't have to set Exists to true, because it is implied. Amazon DynamoDB returns a ValidationException if: Exists is true but there is no Value to check. (You expect a value to exist, but don't specify what that value is.) Exists is false but you also specify a Value. (You cannot expect an attribute to have a value, while also expecting it not to exist.) If you specify more than one condition for Exists, then all of the conditions must evaluate to true. (In other words, the conditions are ANDed together.) Otherwise, the conditional operation will fail.
	Value	Represents the data for an attribute. You can set one, and only one, of the elements.

Name

Description

Exists

Causes Amazon DynamoDB to evaluate the value before attempting a conditional operation:

If Exists is true, Amazon DynamoDB will check to see if that attribute value already exists in the table. If it is found, then the operation succeeds. If it is not found, the operation fails with a ConditionalCheckFailedException.
If Exists is false, Amazon DynamoDB assumes that the attribute value does not exist in the table. If in fact the value does not exist, then the assumption is valid and the operation succeeds. If the value is found, despite the assumption that it does not exist, the operation fails with a ConditionalCheckFailedException.

The default setting for Exists is true. If you supply a Value all by itself, Amazon DynamoDB assumes the attribute exists: You don't have to set Exists to true, because it is implied. Amazon DynamoDB returns a ValidationException if:

Exists is true but there is no Value to check. (You expect a value to exist, but don't specify what that value is.)
Exists is false but you also specify a Value. (You cannot expect an attribute to have a value, while also expecting it not to exist.)

If you specify more than one condition for Exists, then all of the conditions must evaluate to true. (In other words, the conditions are ANDed together.) Otherwise, the conditional operation will fail.

Value

Represents the data for an attribute. You can set one, and only one, of the elements.

Version Information

.NET Framework:
Supported in: 4.5, 4.0, 3.5

.NET for Windows Store apps:
Supported in: Windows 8

.NET for Windows Phone:
Supported in: Window Phone 8

ExpectedAttributeValue Class

Inheritance Hierarchy

Syntax

Constructors

Properties

Version Information