# LS2004: Command Handler Writes Through a Document Session

## Intent

LS2004 is a compiler check that reports a command handler, the type that runs the state change, writing through a document session or database context instead of a repository, which bypasses the boundary that guards the aggregate. This page states what the rule reports, where the error sits, and how to reach stored data through a Domain repository.

## Reference

### What the Rule Enforces

LS2004 enforces [Stage aggregate writes through repositories](https://litespec.dev/4.0.0/backend/dotnet/persistence.md#stage-aggregate-writes-through-repositories) (`litespec/backend/dotnet/persistence#stage-aggregate-writes-through-repositories`). It runs in Application, Infrastructure, and Worker. Its category is `LiteSpec.Layers`. Severity and enablement follow the [Analyzers overview](https://litespec.dev/4.0.0/analyzers/README.md).

### What the Rule Reports

The rule reports a command handler, which is a class whose name ends in `CommandHandler` or that implements `ICommandHandler`, that holds `IDocumentSession`, `DbContext`, or a `DbContext` subclass in a field, property, constructor parameter, or local, or that calls a member through such a receiver. In a declaration the diagnostic sits on the type. In a call it sits on the invoked member name.

### Failing Example

```csharp
internal sealed class PlaceOrderCommandHandler
{
    private readonly IDocumentSession _session = null!;
}
```

### Passing Example

```csharp
internal sealed class PlaceOrderCommandHandler(IOrderRepository orderRepository)
{
    public void Handle(PlaceOrderCommand command)
    {
        var order = Order.Create(command.Quantity);
        orderRepository.Store(order);
    }
}
```

### How to Fix

Reach persistence only through a Domain repository that the handler takes as a constructor parameter.

## Notes

### What the Rule Ignores

The rule does not report handlers that reach persistence only through a Domain repository, or query handlers. It does not run in Domain or WebApi.