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AWS Mobile SDK
Xamarin Developer Guide

Using the Document Model

The Document Model provides wrapper classes around the low-level .NET API. The Table and Document are the key wrapper classes. You can use the Document Model to create, retrieve, update and delete items. To create, update and delete tables, you must use the low-level API. For instructions on how to use the low-level API, see Using the DynamoDB Service Level APIs. The low-level API is available in the Amazon.DynamoDB.DocumentModel namespace.

To learn more about the Document Model, see .NET Document Model.

Create a DynamoDB Client

To create a DynamoDB client:

var client = new AmazonDynamoDBClient(credentials,region); DynamoDBContext context = new DynamoDBContext(client);

CRUD Operations

Save an Item

Create an item:

Table table = Table.LoadTable(client, "Books"); id = Guid.NewGuid().ToString(); var books = new Document(); books["Id"] = id; books["Author"] = "Mark Twain"; books["Title"] = "Adventures of Huckleberry Finn"; books["ISBN"] = "112-111111"; books["Price"] = "10";

Save an item to a DynamoDB table:

var book = await table.PutItemAsync(books);

Retrieve an Item

To retrieve an item:

public async Task GetItemAsync(AWSCredentials credentials, RegionEndpoint region) { var client = new AmazonDynamoDBClient(credentials, region); Table books = Table.LoadTable(client, "Books"); var book = await books.GetItemAsync(id); }

Update an Item

To update an item:

public async Task UpdateItemAttributesAsync(AWSCredentials credentials, RegionEndpoint region) { var book = new Document(); book["Id"] = id; book["PageCount"] = "200"; var client = new AmazonDynamoDBClient(credentials, region); Table books = Table.LoadTable(client, "Books"); Document updatedBook = await books.UpdateItemAsync(book); }

To update an item conditionally:

public async Task UpdateItemConditionallyAsync(AWSCredentials credentials, RegionEndpoint region) { var book = new Document(); book["Id"] = id; book["Price"] = "30"; // For conditional price update, creating a condition expression. Expression expr = new Expression(); expr.ExpressionStatement = "Price = :val"; expr.ExpressionAttributeValues[":val"] = 10.00; var client = new AmazonDynamoDBClient(credentials, region); Table books = Table.LoadTable(client, "Books"); Document updatedBook = await books.UpdateItemAsync(book); }

Delete an Item

To delete an item:

public async Task DeleteItemAsync(AWSCredentials credentials, RegionEndpoint region) { var client = new AmazonDynamoDBClient(credentials, region); Table books = Table.LoadTable(client, "Books"); await books.DeleteItemAsync(id); }

Query and Scan

To query and retrieve all books whose author is "Mark Twain":

public async Task QueryAsync(AWSCredentials credentials, RegionEndpoint region) { var client = new AmazonDynamoDBClient(credentials, region); Table books = Table.LoadTable(client, "Books"); var search = books.Query(new QueryOperationConfig() { IndexName = "Author-Title-index", Filter = new QueryFilter("Author", QueryOperator.Equal, "Mark Twain") }); Console.WriteLine("ScanAsync: printing query response"); var documents = await search.GetRemainingAsync(); documents.ForEach((d) = > { PrintDocument(d); }); }

The scan example code below returns all books in our table:

public async Task ScanAsync(AWSCredentials credentials, RegionEndpoint region) { var client = new AmazonDynamoDBClient(credentials, region); Table books = Table.LoadTable(client, "Books"); var search = books.Scan(new ScanOperationConfig() { ConsistentRead = true }); Console.WriteLine("ScanAsync: printing scan response"); var documents = await search.GetRemainingAsync(); documents.ForEach((d) = > { PrintDocument(d); }); }