Field Configuration¶

Field configuration is handled through [DynamoField] attributes on the mapper class. These attributes target model properties and allow you to override defaults without touching your domain models.

Basic Usage¶

using LayeredCraft.DynamoMapper.Runtime;

[DynamoMapper]
[DynamoField(nameof(Product.Name), AttributeName = "productName", Required = true)]
[DynamoField(nameof(Product.Description), OmitIfNull = true, OmitIfEmptyString = true)]
public static partial class ProductMapper
{
    public static partial Dictionary<string, AttributeValue> ToItem(Product source);
    public static partial Product FromItem(Dictionary<string, AttributeValue> item);
}

Nested Property Overrides (Dot Notation)¶

Use dot notation to override nested properties without adding attributes to nested types:

[DynamoMapper]
[DynamoField("ShippingAddress.Line1", AttributeName = "addr_line1")]
[DynamoField("ShippingAddress.City", AttributeName = "addr_city")]
public static partial class OrderMapper
{
    public static partial Dictionary<string, AttributeValue> ToItem(Order source);
    public static partial Order FromItem(Dictionary<string, AttributeValue> item);
}

Notes:

Dot-notation overrides force inline mapping for the nested path.
Invalid paths emit DM0008.
OmitIfNull works on nested object and nested collection properties too, so paths like "Customer.Profile" or "Customer.Addresses" can omit null containers during ToItem.

Collection Element Members¶

The same dot-notation syntax works when the intermediate segment is a collection (List<T>, T[], Dictionary<string, T>, etc.). The path traverses into the element type of the collection:

[DynamoMapper]
[DynamoField("Contacts.VerifiedAt", Format = "yyyy-MM-dd")]
[DynamoField("Contacts.Name", AttributeName = "contact_name")]
public static partial class CustomerMapper
{
    public static partial Dictionary<string, AttributeValue> ToItem(Customer source);
    public static partial Customer FromItem(Dictionary<string, AttributeValue> item);
}

public class Customer
{
    public string Id { get; set; }
    public List<CustomerContact> Contacts { get; set; }
}

public class CustomerContact
{
    public string Name { get; set; }
    public DateTime VerifiedAt { get; set; }
}

Notes:

The override applies to every element in the collection — there is no per-index syntax.
An invalid property name on the element type still emits DM0008.
Dictionary value types are also supported: "ProductMap.CreatedAt" targets CreatedAt on the value type of Dictionary<string, OrderItem>.

Supported Options¶

Option	Description
`AttributeName`	Overrides the DynamoDB attribute name.
`Required`	Controls requiredness during `FromItem`.
`Kind`	Forces a specific `DynamoKind`.
`OmitIfNull`	Omits null values during `ToItem`, including nested object and nested collection properties.
`OmitIfEmptyString`	Omits empty strings during `ToItem`.
`ToMethod`	Uses a custom method to serialize a value.
`FromMethod`	Uses a custom method to deserialize a value.
`Format`	Overrides default format for date/time/enum conversions.