AWS SDK Version 3 for .NET
API Reference

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Container for the parameters to the UpdateItem operation. Edits an existing item's attributes, or adds a new item to the table if it does not already exist. You can put, delete, or add attribute values. You can also perform a conditional update on an existing item (insert a new attribute name-value pair if it doesn't exist, or replace an existing name-value pair if it has certain expected attribute values).

You can also return the item's attribute values in the same UpdateItem operation using the ReturnValues parameter.

Inheritance Hierarchy

System.Object
  Amazon.Runtime.AmazonWebServiceRequest
    Amazon.DynamoDBv2.AmazonDynamoDBRequest
      Amazon.DynamoDBv2.Model.UpdateItemRequest

Namespace: Amazon.DynamoDBv2.Model
Assembly: AWSSDK.DynamoDBv2.dll
Version: 3.x.y.z

Syntax

C#
public class UpdateItemRequest : AmazonDynamoDBRequest
         IAmazonWebServiceRequest

The UpdateItemRequest type exposes the following members

Constructors

NameDescription
Public Method UpdateItemRequest()

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

Public Method UpdateItemRequest(string, Dictionary<String, AttributeValue>, Dictionary<String, AttributeValueUpdate>)

Instantiates UpdateItemRequest with the parameterized properties

Public Method UpdateItemRequest(string, Dictionary<String, AttributeValue>, Dictionary<String, AttributeValueUpdate>, ReturnValue)

Instantiates UpdateItemRequest with the parameterized properties

Properties

NameTypeDescription
Public Property AttributeUpdates System.Collections.Generic.Dictionary<System.String, Amazon.DynamoDBv2.Model.AttributeValueUpdate>

Gets and sets the property AttributeUpdates.

This is a legacy parameter. Use UpdateExpression instead. For more information, see AttributeUpdates in the Amazon DynamoDB Developer Guide.

Public Property ConditionalOperator Amazon.DynamoDBv2.ConditionalOperator

Gets and sets the property ConditionalOperator.

This is a legacy parameter. Use ConditionExpression instead. For more information, see ConditionalOperator in the Amazon DynamoDB Developer Guide.

Public Property ConditionExpression System.String

Gets and sets the property ConditionExpression.

A condition that must be satisfied in order for a conditional update to succeed.

An expression can contain any of the following:

  • Functions:

    attribute_exists | attribute_not_exists | attribute_type | contains
                | begins_with | size
    

    These function names are case-sensitive.

  • Comparison operators:

    = | <> | < | > | <= | >= | BETWEEN |
                IN 
    

  • Logical operators: AND | OR | NOT

For more information on condition expressions, see Specifying Conditions in the Amazon DynamoDB Developer Guide.

Public Property Expected System.Collections.Generic.Dictionary<System.String, Amazon.DynamoDBv2.Model.ExpectedAttributeValue>

Gets and sets the property Expected.

This is a legacy parameter. Use ConditionExpression instead. For more information, see Expected in the Amazon DynamoDB Developer Guide.

Public Property ExpressionAttributeNames System.Collections.Generic.Dictionary<System.String, System.String>

Gets and sets the property ExpressionAttributeNames.

One or more substitution tokens for attribute names in an expression. The following are some use cases for using ExpressionAttributeNames:

  • To access an attribute whose name conflicts with a DynamoDB reserved word.

  • To create a placeholder for repeating occurrences of an attribute name in an expression.

  • To prevent special characters in an attribute name from being misinterpreted in an expression.

Use the # character in an expression to dereference an attribute name. For example, consider the following attribute name:

  • Percentile

The name of this attribute conflicts with a reserved word, so it cannot be used directly in an expression. (For the complete list of reserved words, see Reserved Words in the Amazon DynamoDB Developer Guide). To work around this, you could specify the following for ExpressionAttributeNames:

  • {"#P":"Percentile"}

You could then use this substitution in an expression, as in this example:

  • #P = :val

Tokens that begin with the : character are expression attribute values, which are placeholders for the actual value at runtime.

For more information on expression attribute names, see Accessing Item Attributes in the Amazon DynamoDB Developer Guide.

Public Property ExpressionAttributeValues System.Collections.Generic.Dictionary<System.String, Amazon.DynamoDBv2.Model.AttributeValue>

Gets and sets the property ExpressionAttributeValues.

One or more values that can be substituted in an expression.

Use the : (colon) character in an expression to dereference an attribute value. For example, suppose that you wanted to check whether the value of the ProductStatus attribute was one of the following:

Available | Backordered | Discontinued

You would first need to specify ExpressionAttributeValues as follows:

{ ":avail":{"S":"Available"}, ":back":{"S":"Backordered"}, ":disc":{"S":"Discontinued"}
            }

You could then use these values in an expression, such as this:

ProductStatus IN (:avail, :back, :disc)

For more information on expression attribute values, see Specifying Conditions in the Amazon DynamoDB Developer Guide.

Public Property Key System.Collections.Generic.Dictionary<System.String, Amazon.DynamoDBv2.Model.AttributeValue>

Gets and sets the property Key.

The primary key of the item to be updated. Each element consists of an attribute name and a value for that attribute.

For the primary key, you must provide all of the attributes. For example, with a simple primary key, you only need to provide a value for the partition key. For a composite primary key, you must provide values for both the partition key and the sort key.

Public Property ReturnConsumedCapacity Amazon.DynamoDBv2.ReturnConsumedCapacity

Gets and sets the property ReturnConsumedCapacity.

Public Property ReturnItemCollectionMetrics Amazon.DynamoDBv2.ReturnItemCollectionMetrics

Gets and sets the property ReturnItemCollectionMetrics.

Determines whether item collection metrics are returned. If set to SIZE, the response includes statistics about item collections, if any, that were modified during the operation are returned in the response. If set to NONE (the default), no statistics are returned.

Public Property ReturnValues Amazon.DynamoDBv2.ReturnValue

Gets and sets the property ReturnValues.

Use ReturnValues if you want to get the item attributes as they appear before or after they are updated. For UpdateItem, the valid values are:

  • NONE - If ReturnValues is not specified, or if its value is NONE, then nothing is returned. (This setting is the default for ReturnValues.)

  • ALL_OLD - Returns all of the attributes of the item, as they appeared before the UpdateItem operation.

  • UPDATED_OLD - Returns only the updated attributes, as they appeared before the UpdateItem operation.

  • ALL_NEW - Returns all of the attributes of the item, as they appear after the UpdateItem operation.

  • UPDATED_NEW - Returns only the updated attributes, as they appear after the UpdateItem operation.

There is no additional cost associated with requesting a return value aside from the small network and processing overhead of receiving a larger response. No read capacity units are consumed.

The values returned are strongly consistent.

Public Property TableName System.String

Gets and sets the property TableName.

The name of the table containing the item to update.

Public Property UpdateExpression System.String

Gets and sets the property UpdateExpression.

An expression that defines one or more attributes to be updated, the action to be performed on them, and new value(s) for them.

The following action values are available for UpdateExpression.

  • SET - Adds one or more attributes and values to an item. If any of these attribute already exist, they are replaced by the new values. You can also use SET to add or subtract from an attribute that is of type Number. For example:

    SET
                myNum = myNum + :val
    

    SET supports the following functions:

    • if_not_exists (path, operand) - if the item does not contain an attribute at the specified path, then if_not_exists evaluates to operand; otherwise, it evaluates to path. You can use this function to avoid overwriting an attribute that may already be present in the item.

    • list_append (operand, operand) - evaluates to a list with a new element added to it. You can append the new element to the start or the end of the list by reversing the order of the operands.

    These function names are case-sensitive.

  • REMOVE - Removes one or more attributes from an item.

  • ADD - Adds the specified value to the item, if the attribute does not already exist. If the attribute does exist, then the behavior of ADD depends on the data type of the attribute:

    • If the existing attribute is a number, and if Value is also a number, then Value is mathematically added to the existing attribute. If Value is a negative number, then it is subtracted from the existing attribute.

      If you use ADD to increment or decrement a number value for an item that doesn't exist before the update, DynamoDB uses 0 as the initial value.

      Similarly, if you use ADD for an existing item to increment or decrement an attribute value that doesn't exist before the update, DynamoDB uses 0 as the initial value. For example, suppose that the item you want to update doesn't have an attribute named itemcount, but you decide to ADD the number 3 to this attribute anyway. DynamoDB will create the itemcount attribute, set its initial value to 0, and finally add 3 to it. The result will be a new itemcount attribute in the item, with a value of 3.

    • If the existing data type is a set and if Value is also a set, then Value is added to the existing set. For example, if the attribute value is the set [1,2], and the ADD action specified [3], then the final attribute value is [1,2,3]. An error occurs if an ADD action is specified for a set attribute and the attribute type specified does not match the existing set type.

      Both sets must have the same primitive data type. For example, if the existing data type is a set of strings, the Value must also be a set of strings.

    The ADD action only supports Number and set data types. In addition, ADD can only be used on top-level attributes, not nested attributes.

  • DELETE - Deletes an element from a set.

    If a set of values is specified, then those values are subtracted from the old set. For example, if the attribute value was the set [a,b,c] and the DELETE action specifies [a,c], then the final attribute value is [b]. Specifying an empty set is an error.

    The DELETE action only supports set data types. In addition, DELETE can only be used on top-level attributes, not nested attributes.

You can have many actions in a single expression, such as the following:

SET
            a=:value1, b=:value2 DELETE :value3, :value4, :value5

For more information on update expressions, see Modifying Items and Attributes in the Amazon DynamoDB Developer Guide.

Examples

This example shows how to update an item in a table.

UpdateItem sample


// Create a client
AmazonDynamoDBClient client = new AmazonDynamoDBClient();

// Define item key
//  Hash-key of the target item is string value "Mark Twain"
//  Range-key of the target item is string value "The Adventures of Tom Sawyer"
Dictionary key = new Dictionary
{
    { "Author", new AttributeValue { S = "Mark Twain" } },
    { "Title", new AttributeValue { S = "The Adventures of Tom Sawyer" } }
};

// Define attribute updates
Dictionary updates = new Dictionary();
// Update item's Setting attribute
updates["Setting"] = new AttributeValueUpdate()
{
    Action = AttributeAction.PUT,
    Value = new AttributeValue { S = "St. Petersburg, Missouri" }
};
// Remove item's Bibliography attribute
updates["Bibliography"] = new AttributeValueUpdate()
{
    Action = AttributeAction.DELETE
};   
// Add a new string to the item's Genres SS attribute
updates["Genres"] = new AttributeValueUpdate()
{
    Action = AttributeAction.ADD,
    Value = new AttributeValue { SS = new List { "Bildungsroman" } }
};

// Create UpdateItem request
UpdateItemRequest request = new UpdateItemRequest
{
    TableName = "SampleTable",
    Key = key,
    AttributeUpdates = updates
};

// Issue request
client.UpdateItem(request);

                

Version Information

.NET Standard:
Supported in: 1.3

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

Portable Class Library:
Supported in: Windows Store Apps
Supported in: Windows Phone 8.1
Supported in: Xamarin Android
Supported in: Xamarin iOS (Unified)
Supported in: Xamarin.Forms

Unity:
Supported Versions: 4.6 and above
Supported Platforms: Android, iOS, Standalone