Entity Framework Transactions

Transactions are a fundamental concept in database management, ensuring that a series of database operations are treated as a single, atomic unit. Either all operations within the transaction succeed, or none of them do. This maintains data integrity and consistency. Entity Framework Core (EF Core) provides robust support for managing transactions.

Understanding Transactions in EF Core

By default, EF Core executes each operation (like calling SaveChanges()) within its own implicit transaction. If the operation fails, EF Core automatically rolls back the changes. However, for scenarios where you need to perform multiple operations atomically, you can explicitly manage transactions.

Explicit Transactions

To control transactions explicitly, you can use the Database.BeginTransaction() method on your DbContext. This returns a transaction object that you can then use to control the transaction's lifecycle.

Starting a Transaction


using (var context = new MyDbContext())
{
    using (var transaction = context.Database.BeginTransaction())
    {
        try
        {
            // Perform database operations here
            var user = new User { Name = "Alice" };
            context.Users.Add(user);
            context.SaveChanges();

            var product = new Product { Name = "Widget", Price = 19.99m };
            context.Products.Add(product);
            context.SaveChanges();

            // If all operations succeed, commit the transaction
            transaction.Commit();
            Console.WriteLine("Transaction committed successfully.");
        }
        catch (Exception ex)
        {
            // If any operation fails, roll back the transaction
            transaction.Rollback();
            Console.WriteLine($"Transaction rolled back: {ex.Message}");
            // Re-throw the exception if necessary
            // throw;
        }
    }
}

Committing and Rolling Back

transaction.Commit(): Makes all the changes within the transaction permanent.
transaction.Rollback(): Undoes all the changes made within the transaction.

It's crucial to wrap your transactional operations in a try-catch block. If an exception occurs during any of the operations, the catch block will execute, allowing you to call transaction.Rollback() to ensure data consistency.

Best Practice: Always use a using statement for both the DbContext and the DbTransaction to ensure they are properly disposed of, even if errors occur.

Transaction Isolation Levels

EF Core allows you to specify the isolation level for your transactions. The isolation level determines how and when the results of one transaction are visible to other concurrent transactions. Common isolation levels include:

ReadCommitted (default for most databases)
ReadUncommitted
RepeatableRead
Serializable

You can specify the isolation level when starting a transaction:


using (var context = new MyDbContext())
{
    var transactionOptions = new TransactionOptions
    {
        IsolationLevel = System.Transactions.IsolationLevel.Serializable
    };

    using (var transaction = context.Database.BeginTransaction(transactionOptions))
    {
        // ... your transactional code ...
    }
}

The available isolation levels depend on the underlying database provider.

Note: Higher isolation levels provide stronger consistency but can reduce concurrency and potentially lead to deadlocks. Choose the isolation level that best suits your application's needs.

Distributed Transactions

For scenarios involving multiple databases or services that need to participate in a single atomic operation, EF Core supports distributed transactions using System.Transactions. This typically involves using a transaction coordinator.


using (var transactionScope = new System.Transactions.TransactionScope())
{
    using (var context1 = new DbContextA())
    {
        // Operations on DbContextA
        context1.SaveChanges();
    }

    using (var context2 = new DbContextB())
    {
        // Operations on DbContextB
        context2.SaveChanges();
    }

    // If all is well, complete the transaction
    transactionScope.Complete();
}

TransactionScope automatically enlists supported resources (like databases via their transaction managers) into a distributed transaction. Calling Complete() signifies that the transaction was successful.

Managing distributed transactions can be complex and requires careful consideration of resource enlistment and failure handling.

When to Use Explicit Transactions

When a business operation involves multiple distinct database writes that must succeed or fail together.
To maintain data integrity across related entities that are saved in separate SaveChanges() calls.
When implementing complex workflows that require atomicity.

By effectively using transactions, you can build more robust and reliable data-driven applications with Entity Framework Core.