How to handle transactions between several generic IRepositories

Question

What is a good practice on work with (nHibernate) ITransactions between several repositories?

First created a BeginTransaction() on the generic interface, but i then come to think about how will this work between the repositories? i mean if a delete things from on repository and then other things from another repository, but want's to wrap the whole operation in a transaction.

although all the reposistories share the same ISession (handled by the DI framework) so i guess could get a ITransaction from any of the repositories and then commit it, and it will work for all the other repositories as well.

Answer 1

By not making the repository responsible for the transaction management. Do not inject ISession directly in the repository, but use a unit of work that holds the session and starts and commits the transaction.

INHibernateUnitOfWork
{
   ISession CurrentSession { get; }
   void Start(); // begins the transaction
   void Commit();
   void RollBack();
}

Answer 2

I could instead of making the whole class generic, just make each function generic, like this:

public interface IRepository
{
    T Get<T>(int id);
    T SingleOrDefault<T>(Func<T, bool> query);
    IQueryable<T> Where<T>(Expression<Func<T, bool>> query);
    IQueryable<T> All<T>();
    void Save<T>(T entity);
    void Delete<T>(T entity);
    ITransaction BeginTransaction();
}

but then the interface is more or less depended on nHibernate anyway, so maybe it's worth implementering the Unit of Work pattern after all.