Working with the .NET object persistence model and DynamoDB

The AWS SDK for .NET provides an object persistence model that enables you to map your client-side classes to Amazon DynamoDB tables. Each object instance then maps to an item in the corresponding tables. To save your client-side objects to the tables, the object persistence model provides the DynamoDBContext class, an entry point to DynamoDB. This class provides you a connection to DynamoDB and enables you to access tables, perform various CRUD operations, and run queries.

The object persistence model provides a set of attributes to map client-side classes to tables, and properties/fields to table attributes.

The following example shows how the object persistence model works. It starts with the ProductCatalog table. It has Id as the primary key.

ProductCatalog(Id, ...)

Suppose that you have a Book class with Title, ISBN, and Authors properties. You can map the Book class to the ProductCatalog table by adding the attributes defined by the object persistence model, as shown in the following C# code example.

[DynamoDBTable("ProductCatalog")]
  public class Book
  {
    [DynamoDBHashKey]
    public int Id { get; set; }

    public string Title { get; set; }
    public int ISBN { get; set; }

    [DynamoDBProperty("Authors")]
    public List<string> BookAuthors { get; set; }

    [DynamoDBIgnore]
    public string CoverPage { get; set; }
  }

In the preceding example, the DynamoDBTable attribute maps the Book class to the ProductCatalog table.

The object persistence model supports both the explicit and default mapping between class properties and table attributes.

You don't have to map every single class property. You identify these properties by adding the DynamoDBIgnore attribute. When you save a Book instance to the table, the DynamoDBContext does not include the CoverPage property. It also does not return this property when you retrieve the book instance.

You can map properties of .NET primitive types such as int and string. You also can map any arbitrary data types as long as you provide an appropriate converter to map the arbitrary data to one of the DynamoDB types. To learn about mapping arbitrary types, see Mapping arbitrary data with DynamoDB using the AWS SDK for .NET object persistence model.

The object persistence model supports optimistic locking. During an update operation, this ensures that you have the latest copy of the item you are about to update. For more information, see Optimistic locking using DynamoDB and the AWS SDK for .NET object persistence model.

For more information, see the topics below.

Supported data types

The object persistence model supports a set of primitive .NET data types, collections, and arbitrary data types. The model supports the following primitive data types.

The object persistence model also supports the .NET collection types. DynamoDBContext is able to convert concrete collection types and simple Plain Old CLR Objects (POCOs).

The following table summarizes the mapping of the preceding .NET types to the DynamoDB types.

The object persistence model also supports arbitrary data types. However, you must provide converter code to map the complex types to the DynamoDB types.