Attributes¶

DynamoMapper configuration is done via attributes on the mapper class.

DynamoMapperAttribute¶

Marks a static partial class as a mapper and sets defaults.

[DynamoMapper(
    Convention = DynamoNamingConvention.CamelCase,
    DefaultRequiredness = Requiredness.InferFromNullability,
    IncludeBaseClassProperties = false,
    OmitNullValues = true,
    OmitEmptyStrings = false,
    DateTimeFormat = "O",
    EnumFormat = "G")]
public static partial class OrderMapper
{
    public static partial Dictionary<string, AttributeValue> ToItem(Order source);
    public static partial Order FromItem(Dictionary<string, AttributeValue> item);
}

Properties:

• Convention - key naming convention
• DefaultRequiredness - default requiredness
• IncludeBaseClassProperties - include properties declared on base classes (opt-in)
• OmitNullValues - omit null values, including nested object and nested collection properties
• OmitNullStrings - deprecated legacy option kept for compatibility with helper-backed null omission
• OmitEmptyStrings - omit empty string attributes
• DateTimeFormat - DateTime/DateTimeOffset format
• TimeSpanFormat - TimeSpan format
• EnumFormat - enum format
• GuidFormat - Guid format

Notes:

• When IncludeBaseClassProperties = true, inherited properties are included for root models and nested inline objects.
• If a derived type declares a property with the same name as an inherited property, the derived property wins.
• Prefer OmitNullValues for mapper-level null omission. OmitNullStrings remains available only as a legacy compatibility option.

DynamoFieldAttribute¶

Configures mapping for a specific member. Apply multiple times to the mapper class.

[DynamoMapper]
[DynamoField(nameof(Order.Notes), OmitIfNull = true, OmitIfEmptyString = true)]
[DynamoField(nameof(Order.OrderId), AttributeName = "orderId")]
public static partial class OrderMapper
{
    public static partial Dictionary<string, AttributeValue> ToItem(Order source);
    public static partial Order FromItem(Dictionary<string, AttributeValue> item);
}

Properties:

• MemberName (ctor) - target member name
• AttributeName - DynamoDB attribute name override
• Required - requiredness override
• Kind - DynamoDB DynamoKind override
• OmitIfNull - omit when null, including nested object and nested collection properties
• OmitIfEmptyString - omit when empty string
• ToMethod / FromMethod - static conversion methods on the mapper class

DynamoIgnoreAttribute¶

Skips a member in one or both directions.

[DynamoMapper]
[DynamoIgnore(nameof(Order.InternalNotes), Ignore = IgnoreMapping.All)]
public static partial class OrderMapper
{
    public static partial Dictionary<string, AttributeValue> ToItem(Order source);
    public static partial Order FromItem(Dictionary<string, AttributeValue> item);
}

Properties:

• MemberName (ctor) - target member name
• Ignore - IgnoreMapping.All, IgnoreMapping.FromModel, or IgnoreMapping.ToModel

DynamoMapperConstructorAttribute¶

Marks which constructor DynamoMapper should use when generating FromItem for a model type.

This attribute is applied to the model's constructor, not the mapper class.

using LayeredCraft.DynamoMapper.Runtime;

public class User
{
    public User()
    {
        Id = string.Empty;
        Name = string.Empty;
    }

    [DynamoMapperConstructor]
    public User(string id, string name)
    {
        Id = id;
        Name = name;
    }

    public string Id { get; set; }
    public string Name { get; set; }
}

Rules:

• Only one constructor can be marked with [DynamoMapperConstructor].
• If multiple are marked, DynamoMapper emits diagnostic DM0103.

See Basic Mapping for the full constructor selection rules and gotchas.