Unit of Work

Maintains a list of operations affected by a business transaction and coordinates their writing.

Context

A business operation modifies multiple aggregates (Order, Inventory, Audit). You want to commit ALL or nothing.

Problem

Without coordination, you might save the order but fail to decrement stock.

Solution

A UnitOfWork groups operations and commits them with SaveChanges() within a single transaction.

#Example in C#

public interface IUnitOfWork : IAsyncDisposable
{
    IOrderRepository Orders { get; }
    IInventoryRepository Inventory { get; }
    Task<int> SaveChangesAsync(CancellationToken ct = default);
}

public class EfUnitOfWork : IUnitOfWork
{
    private readonly AppDbContext _db;
    public EfUnitOfWork(AppDbContext db, IOrderRepository o, IInventoryRepository i)
    { _db = db; Orders = o; Inventory = i; }

    public IOrderRepository Orders { get; }
    public IInventoryRepository Inventory { get; }

    public Task<int> SaveChangesAsync(CancellationToken ct = default) => _db.SaveChangesAsync(ct);
    public ValueTask DisposeAsync() => _db.DisposeAsync();
}

// Usage
await using var uow = factory.Create();
uow.Orders.Add(order);
uow.Inventory.Reserve(order.Items);
await uow.SaveChangesAsync();

In EF Core, DbContext is already a Unit of Work. Creating another one on top is usually redundant.

When NOT to use it

If your ORM already implements Unit of Work (EF, NHibernate).
If operations span processes (in which case you need Saga / Outbox).

#extra #persistence #transaction