Entity Contracts

Serenity uses marker interfaces (contracts) to give a row special capabilities. By implementing one of these interfaces, your row tells the framework "I have an ID field", "I support soft delete", "I have logging fields", etc. — and the corresponding behaviors, handlers, and UI features activate automatically.

Identity & Name

IIdRow — the row has an ID field. Put [IdProperty] on the corresponding field. This is the most common contract; most rows implement it.
INameRow — the row has a name/description field. Put [NameProperty] on the corresponding field. Used for the row's display title and quick search.
IDisplayNameRow — exposes a DisplayNameField (a StringField).

public sealed class PersonRow : Row<PersonRow.RowFields>, IIdRow, INameRow
{
    [DisplayName("Person Id"), Identity, IdProperty]
    public int? PersonId { get => fields.PersonId[this]; set => fields.PersonId[this] = value; }

    [DisplayName("Full Name"), NameProperty]
    public string FullName { get => fields.FullName[this]; set => fields.FullName[this] = value; }
}

Active / Deleted (Soft Delete)

IIsActiveRow — the row has an IsActiveField (Int16Field). 1 = active, 0 = inactive.
IIsActiveDeletedRow — an IIsActiveRow where -1 means deleted (soft delete via the active flag).
IIsDeletedRow — the row has an IsDeletedField (BooleanField) for soft delete.

Rows implementing these are not physically deleted — the delete handler sets the flag instead, and list queries filter out deleted rows.

Logging Fields

IInsertDateRow — has an InsertDateField.
IInsertUserIdRow — has an InsertUserIdField.
IUpdateDateRow — has an UpdateDateField.
IUpdateUserIdRow — has an UpdateUserIdField.
IInsertLogRow — combination of IInsertDateRow + IInsertUserIdRow.
IUpdateLogRow — combination of IUpdateDateRow + IUpdateUserIdRow.
ILoggingRow — combination of IUpdateLogRow + IInsertLogRow. This is the one you implement for full insert/update audit logging.
IDeleteLogRow — has DeleteUserIdField and DeleteDateField (delete audit logging).

The UpdateInsertLogBehavior fills these fields automatically on save. See Built-in Service Behaviors.

Ordering & Hierarchy

IDisplayOrderRow — has a DisplayOrderField (Int32Field); the row is kept in order automatically.
IParentIdRow — has a ParentIdField; used for tree/hierarchical rows and parent validation.

Other Contracts

IEmailRow — exposes an EmailField (used by membership/account features).
IPasswordRow — exposes PasswordHashField and PasswordSaltField (used by authentication).
IFieldWithJoinInfo — a field that exposes its referenced aliases and the row's joins (used by query building).

How Contracts Are Used

These interfaces are what make the framework's conventions work:

Request handlers check for IIdRow to know the ID field, INameRow for the name field, IIsActiveRow/IIsDeletedRow for soft delete, ILoggingRow for audit fields.
Behaviors activate based on these interfaces (e.g. CaptureLogBehavior requires IIdRow; UpdateInsertLogBehavior activates for logging rows).
The UI uses IIdRow/INameRow for dialog titles, quick search, and lookup scripts.

Implementing a contract is usually just adding the interface to the row declaration and marking the corresponding field with the matching attribute ([IdProperty], [NameProperty], etc.).