# Transaction Pattern

> Part of `Mango.Nop.Data`. See `Mango.Nop.Data/README.md` for project overview.
> For repository base classes see `docs/REPOSITORIES.md`.

## MgDbContextBase

Abstract database context base. NOT an EF Core DbContext — wraps `INopDataProvider` and `IRepository<T>` nopCommerce repos.

**Constructor:**
```csharp
MgDbContextBase(IRepository<Product>, IRepository<Order>, IRepository<OrderItem>, INopDataProvider, IMgLockService, ILogger)
```

### Standard Repositories

| Property | Type |
|---|---|
| `Orders` | `IRepository<Order>` |
| `OrderItems` | `IRepository<OrderItem>` |
| `Products` | `IRepository<Product>` |
| `DataProvider` | `INopDataProvider` (LinqToDB raw queries) |
| `Logger` | Mango `ILogger` |
| `LockService` | `IMgLockService` (global `SemaphoreSlim`) |

### 4 Transaction Methods

| Method | Lock | Async |
|---|---|---|
| `Transaction(callback)` | No | No |
| `TransactionSafe(callback)` | `SemaphoreSlim` | No |
| `TransactionAsync(callback)` | No | Yes (thread pool) |
| `TransactionSafeAsync(callback)` | `SemaphoreSlim` | Yes (thread pool) |

**Callback contract:** `Func<TransactionScope, (Task<)bool(>)>` — return `true` to commit (`Complete()`), `false` to rollback.

**Isolation level:** `ReadCommitted`

**Error handling:** Catches exceptions, logs, returns `false` (unless `throwException = true`).

**TransactionSafe variants:** Use `LockService.SemaphoreSlim` for global serialization. Use for order creation, stock adjustment — any operation where concurrent modifications would corrupt data.

**Async variants:** Run on thread pool via `TaskHelper.ToThreadPoolTask()`.

## MgDalBase\<TDbContext\>

Data Access Layer orchestrator. Thin wrapper exposing:

| Property | Type | Purpose |
|---|---|---|
| `Name` | `string` | DAL instance name |
| `Context` | `TDbContext` | The DB context (typed) |
| `MutextLock` | `Mutex` | Cross-process locking |