Class ExpectedAttributeValue

Namespace: Amazon.DynamoDBv2.Model

Assembly: AWSSDK.DynamoDBv2.dll

Represents a condition to be compared with an attribute value. This condition can be used with

DeleteItem

PutItem

, or

UpdateItem

operations; if the comparison evaluates to true, the operation succeeds; if not, the operation fails. You can use

ExpectedAttributeValue

in one of two different ways:

Use
```
AttributeValueList
```
to specify one or more values to compare against an attribute. Use
```
ComparisonOperator
```
to specify how you want to perform the comparison. If the comparison evaluates to true, then the conditional operation succeeds.
Use
```
Value
```
to specify a value that DynamoDB will compare against an attribute. If the values match, then
```
ExpectedAttributeValue
```
evaluates to true and the conditional operation succeeds. Optionally, you can also set
```
Exists
```
to false, indicating that you do not expect to find the attribute value in the table. In this case, the conditional operation succeeds only if the comparison evaluates to false.

Value

and

Exists

are incompatible with

AttributeValueList

and

ComparisonOperator

. Note that if you use both sets of parameters at once, DynamoDB will return a

ValidationException

exception.

public class ExpectedAttributeValue

Inheritance: object

ExpectedAttributeValue

Inherited Members: object.GetType()

object.MemberwiseClone()

object.ToString()

object.Equals(object)

object.Equals(object, object)

object.ReferenceEquals(object, object)

object.GetHashCode()

Constructors

ExpectedAttributeValue()

Empty constructor used to set properties independently even when a simple constructor is available

public ExpectedAttributeValue()

ExpectedAttributeValue(AttributeValue)

Instantiates ExpectedAttributeValue with the parameterized properties

public ExpectedAttributeValue(AttributeValue value)

Parameters

value AttributeValue: Represents the data for the expected attribute. Each attribute value is described as a name-value pair. The name is the data type, and the value is the data itself. For more information, see Data Types in the Amazon DynamoDB Developer Guide.

ExpectedAttributeValue(bool)

Instantiates ExpectedAttributeValue with the parameterized properties

public ExpectedAttributeValue(bool exists)

Parameters

exists bool

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

If
```
Exists
```
is
```
true
```
, 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
```
ConditionCheckFailedException
```
.
If
```
Exists
```
is
```
false
```
, 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
```
ConditionCheckFailedException
```
.

The default setting for

Exists

true

. If you supply a

Value

all by itself, DynamoDB assumes the attribute exists: You don't have to set

Exists

true

, because it is implied. 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 provide a
```
Value
```
. (You cannot expect an attribute to have a value, while also expecting it not to exist.)

Properties

AttributeValueList

Gets and sets the property AttributeValueList.

One or more values to evaluate against the supplied attribute. The number of values in the list depends on the

ComparisonOperator

being used.

For type Number, value comparisons are numeric.

String value comparisons for greater than, equals, or less than are based on ASCII character code values. For example,

is greater than

, and

is greater than

. For a list of code values, see http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters.

For Binary, DynamoDB treats each byte of the binary data as unsigned when it compares binary values.

For information on specifying data types in JSON, see JSON Data Format in the Amazon DynamoDB Developer Guide.

public List<AttributeValue> AttributeValueList { get; set; }

Property Value

List<AttributeValue>

ComparisonOperator

Gets and sets the property ComparisonOperator.

A comparator for evaluating attributes in the

AttributeValueList

. For example, equals, greater than, less than, etc.

The following comparison operators are available:

EQ | NE | LE | LT | GE | GT | NOT_NULL | NULL | CONTAINS | NOT_CONTAINS | BEGINS_WITH
                   | IN | BETWEEN

The following are descriptions of each comparison operator.

```
EQ
```
: Equal.
```
EQ
```
is supported for all data types, including lists and maps.
```
AttributeValueList
```
can contain only one
```
AttributeValue
```
element of type String, Number, Binary, String Set, Number Set, or Binary Set. If an item contains an
```
AttributeValue
```
element of a different type than the one provided in the request, the value does not match. For example,
```
{"S":"6"}
```
does not equal
```
{"N":"6"}
```
. Also,
```
{"N":"6"}
```
does not equal
```
{"NS":["6", "2", "1"]}
```
.
```
NE
```
: Not equal.
```
NE
```
is supported for all data types, including lists and maps.
```
AttributeValueList
```
can contain only one
```
AttributeValue
```
of type String, Number, Binary, String Set, Number Set, or Binary Set. If an item contains an
```
AttributeValue
```
of a different type than the one provided in the request, the value does not match. For example,
```
{"S":"6"}
```
does not equal
```
{"N":"6"}
```
. Also,
```
{"N":"6"}
```
does not equal
```
{"NS":["6",
                                                                                          "2", "1"]}
```
.
```
LE
```
: Less than or equal.
```
AttributeValueList
```
can contain only one
```
AttributeValue
```
element of type String, Number, or Binary (not a set type). If an item contains an
```
AttributeValue
```
element of a different type than the one provided in the request, the value does not match. For example,
```
{"S":"6"}
```
does not equal
```
{"N":"6"}
```
. Also,
```
{"N":"6"}
```
does not compare to
```
{"NS":["6",
                                                                                     "2", "1"]}
```
.
```
LT
```
: Less than.
```
AttributeValueList
```
can contain only one
```
AttributeValue
```
of type String, Number, or Binary (not a set type). If an item contains an
```
AttributeValue
```
element of a different type than the one provided in the request, the value does not match. For example,
```
{"S":"6"}
```
does not equal
```
{"N":"6"}
```
. Also,
```
{"N":"6"}
```
does not compare to
```
{"NS":["6", "2", "1"]}
```
.
```
GE
```
: Greater than or equal.
```
AttributeValueList
```
can contain only one
```
AttributeValue
```
element of type String, Number, or Binary (not a set type). If an item contains an
```
AttributeValue
```
element of a different type than the one provided in the request, the value does not match. For example,
```
{"S":"6"}
```
does not equal
```
{"N":"6"}
```
. Also,
```
{"N":"6"}
```
does not compare to
```
{"NS":["6",
                                                                                     "2", "1"]}
```
.
```
GT
```
: Greater than.
```
AttributeValueList
```
can contain only one
```
AttributeValue
```
element of type String, Number, or Binary (not a set type). If an item contains an
```
AttributeValue
```
element of a different type than the one provided in the request, the value does not match. For example,
```
{"S":"6"}
```
does not equal
```
{"N":"6"}
```
. Also,
```
{"N":"6"}
```
does not compare to
```
{"NS":["6",
                                                                                     "2", "1"]}
```
.
```
NOT_NULL
```
: The attribute exists.
```
NOT_NULL
```
is supported for all data types, including lists and maps.
note
This operator tests for the existence of an attribute, not its data type. If the data type of attribute "
```
a
```
" is null, and you evaluate it using
```
NOT_NULL
```
, the result is a Boolean
```
true
```
. This result is because the attribute "
```
a
```
" exists; its data type is not relevant to the
```
NOT_NULL
```
comparison operator.
```
NULL
```
: The attribute does not exist.
```
NULL
```
is supported for all data types, including lists and maps.
note
This operator tests for the nonexistence of an attribute, not its data type. If the data type of attribute "
```
a
```
" is null, and you evaluate it using
```
NULL
```
, the result is a Boolean
```
false
```
. This is because the attribute "
```
a
```
" exists; its data type is not relevant to the
```
NULL
```
comparison operator.
```
CONTAINS
```
: Checks for a subsequence, or value in a set.
```
AttributeValueList
```
can contain only one
```
AttributeValue
```
element of type String, Number, or Binary (not a set type). If the target attribute of the comparison is of type String, then the operator checks for a substring match. If the target attribute of the comparison is of type Binary, then the operator looks for a subsequence of the target that matches the input. If the target attribute of the comparison is a set ("
```
SS
```
", "
```
NS
```
", or "
```
BS
```
"), then the operator evaluates to true if it finds an exact match with any member of the set.
CONTAINS is supported for lists: When evaluating "
```
a CONTAINS b
```
", "
```
a
```
" can be a list; however, "
```
b
```
" cannot be a set, a map, or a list.
```
NOT_CONTAINS
```
: Checks for absence of a subsequence, or absence of a value in a set.
```
AttributeValueList
```
can contain only one
```
AttributeValue
```
element of type String, Number, or Binary (not a set type). If the target attribute of the comparison is a String, then the operator checks for the absence of a substring match. If the target attribute of the comparison is Binary, then the operator checks for the absence of a subsequence of the target that matches the input. If the target attribute of the comparison is a set ("
```
SS
```
", "
```
NS
```
", or "
```
BS
```
"), then the operator evaluates to true if it does not find an exact match with any member of the set.
NOT_CONTAINS is supported for lists: When evaluating "
```
a NOT CONTAINS b
```
", "
```
a
```
" can be a list; however, "
```
b
```
" cannot be a set, a map, or a list.
```
BEGINS_WITH
```
: Checks for a prefix.
```
AttributeValueList
```
can contain only one
```
AttributeValue
```
of type String or Binary (not a Number or a set type). The target attribute of the comparison must be of type String or Binary (not a Number or a set type).
```
IN
```
: Checks for matching elements in a list.
```
AttributeValueList
```
can contain one or more
```
AttributeValue
```
elements of type String, Number, or Binary. These attributes are compared against an existing attribute of an item. If any elements of the input are equal to the item attribute, the expression evaluates to true.
```
BETWEEN
```
: Greater than or equal to the first value, and less than or equal to the second value.
```
AttributeValueList
```
must contain two
```
AttributeValue
```
elements of the same type, either String, Number, or Binary (not a set type). A target attribute matches if the target value is greater than, or equal to, the first element and less than, or equal to, the second element. If an item contains an
```
AttributeValue
```
element of a different type than the one provided in the request, the value does not match. For example,
```
{"S":"6"}
```
does not compare to
```
{"N":"6"}
```
. Also,
```
{"N":"6"}
```
does not compare to
```
{"NS":["6", "2", "1"]}
```

public ComparisonOperator ComparisonOperator { get; set; }

Property Value

ComparisonOperator

Exists

Gets and sets the property Exists.

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

If
```
Exists
```
is
```
true
```
, 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
```
ConditionCheckFailedException
```
.
If
```
Exists
```
is
```
false
```
, 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
```
ConditionCheckFailedException
```
.

The default setting for

Exists

true

. If you supply a

Value

all by itself, DynamoDB assumes the attribute exists: You don't have to set

Exists

true

, because it is implied.

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 provide a
```
Value
```
. (You cannot expect an attribute to have a value, while also expecting it not to exist.)

public bool Exists { get; set; }

Property Value

bool

Value

Gets and sets the property Value.

Represents the data for the expected attribute.

Each attribute value is described as a name-value pair. The name is the data type, and the value is the data itself.

For more information, see Data Types in the Amazon DynamoDB Developer Guide.

public AttributeValue Value { get; set; }

Property Value

AttributeValue

Table of Contents

Class ExpectedAttributeValue

Constructors

ExpectedAttributeValue()

ExpectedAttributeValue(AttributeValue)

Parameters

ExpectedAttributeValue(bool)

Parameters

Properties

AttributeValueList

Property Value

ComparisonOperator

note

note

Property Value

Exists

Property Value

Value

Property Value