# UseInMemory

Adds in-memory database support for testing and development. No external database required. Data is lost when the application shuts down.

## Signature

```csharp
public static TraxEffectBuilderWithData UseInMemory(
    this TraxEffectBuilder effectBuilder
)
```

## Parameters

None.

## Returns

`TraxEffectBuilderWithData`, a subclass of `TraxEffectBuilder` that unlocks data-dependent methods like [AddDataContextLogging](/docs/sdk-reference/configuration/add-effect-data-context-logging). This provides compile-time safety: methods that require a data provider are only available on the returned type.

## Example

```csharp
services.AddTrax(trax => trax
    .AddEffects(effects => effects
        .UseInMemory()
    )
    .AddMediator(typeof(Program).Assembly)
);
```

## Remarks

- Suitable for unit/integration testing and local development.
- Data does not persist between application restarts.
- Registers an `IDataContext` backed by an in-memory EF Core provider.
- For production use, use [UsePostgres](/docs/sdk-reference/configuration/add-postgres-effect) instead.

## Package

```
dotnet add package Trax.Effect.Data.InMemory
```