Database Transactions

All updates to an ice.NET database repository must per performed inside a transaction scope. The transaction ensures that the result of the update are persisted to the database only if the whole transaction has been successfully completed. It also helps to ensure the consistency of data accessed by concurrent sessions.

Any attempt to call a updating method or property outside a transaction scope results in a DatabaseException thrown by the platform.

Examples

This example shows how to use an ITransactionContext to implement an atomic, exception-safe transaction scope.

using (ITransactionContext pTransaction = Repository.BeginTransaction())
{
    try
    {
        // [do some updates, throw exception on failure]...

        // Transaction sucessfully completed...
        pTransaction.Commit();
    }
    catch
    {
        // Transaction failed...
        pTransaction.Rollback();
        throw;
    }
}

This example shows how to use the IDatabaseRepository.ExecuteTransaction convenience method to implement an atomic, exception-safe transaction scope.

Repository.ExecuteTransaction(delegate()
{
    // [do some updates, throw exception on failure]...
});

The commit/rollback handling is done automatically based on wether the IDatabaseRepository.ExecuteTransaction scope is exited regularly or with an exception.

Transactions and Business Objects

Business objects implementations should not actively refer to transaction management. It should always be the calling environment (service, user interface) that defines the scope of a transaction. This is crucial to ensure the usefulness of the business objects in a variety of application cases, not only in the context of a particular business transaction.

By throwing an exception, the business objects implementation can indicate that something went wrong that prevents the encapsulating transaction from being successfully comitted. The transaction itself will be then rolled back as a whole by the calling scope.

In-memory processing

This information about transactions applies to database repositories only. When accessing the in-memory repository implementation (by retrieving an IRepository reference from IInProcRepositoryFactory), transaction management is not available. The transaction management methods are defined in IDatabaseRepository.

However, this does not affect the applicability of business objects in arbitrary repository environments, because the business objects refer to the IRepository interface only and do/should not contain any active transaction handling themselves.