---
title: DomainBase<TItem>
summary: API reference for DomainBase<TItem>.
status: draft
owner: SAIF Doc Gen
last_reviewed: 2026-09-24
library: SAIF.Domain
reference_type: package
---

# DomainBase\<TItem\>

`DomainBase<TItem>` is the root abstraction that every SAIF.Domain wrapper class builds on: it holds the single NHibernate data entity (`TItem`, constrained to `IDataEntity`) that a domain type presents behaviour around, and gives every subclass a uniform, null-safe way to ask whether that entity actually has data. Concrete domain types across the library — including query-provider wrappers (`DomainQueryBase<TItem,TQueryProvider>`) and repository-backed wrappers (`DomainRepositoryBase<TItem>`) — derive from it rather than holding the entity themselves, so this class defines the common shape those two families extend.

## Purpose
- Owns the single `TItem` data entity that a domain wrapper exposes behaviour around, so callers work through the domain type rather than the raw NHibernate entity directly.
- Provides a consistent, null-safe `HasData` check (based on `SAIF.Common` `IsNull()`) so subclasses do not each reimplement entity-presence checks.
- Establishes the constructor contract (`protected DataItem`) that `DomainQueryBase<TItem,TQueryProvider>` and `DomainRepositoryBase<TItem>` build on for query-provider and repository-factory injection respectively.

## Context
- Namespace: `SAIF.Domain`
- Assembly/package: `SAIF.Domain` (`Domain/SAIF.Domain/SAIF.Domain.csproj`, .NET Framework 4.6.2 class library)

## Public members
| Member | Signature | Purpose |
| --- | --- | --- |
| DomainBase (constructor) | `protected DomainBase(TItem data)` | Initializes the wrapper with the backing data entity that subclass behaviour operates on. |
| DomainBase (parameterless constructor) | `internal DomainBase()` | Internal-only constructor reserved for framework/test scaffolding*; not intended for library consumers to call directly. |
| HasData | `public virtual bool HasData { get; }` | Reports whether the wrapped entity is present, evaluated as `!DataItem.IsNull()` so callers can guard behaviour without null-reference risk. |
| DataItem | `protected TItem DataItem { get; set; }` | The backing NHibernate data entity that subclass methods read and mutate to implement domain behaviour. |

## Behavioral notes
- `HasData` is declared `virtual`, so a subclass can override the presence check if its notion of "has data" differs from simple null-checking*.
- The parameterless `internal DomainBase()` constructor bypasses entity assignment entirely; any subclass relying on it must set `DataItem` itself before use**.

> **Note:** Statements marked with `*` were inferred from code structure, naming conventions, or
> contextual evidence where direct confirmation was not available in source artifacts. Statements
> marked with `**` could not be confirmed; treat as unknown until verified.

## Sources
- `Domain/SAIF.Domain/DomainBase.cs`
- `Domain/SAIF.Domain/SAIF.Domain.csproj`