var options = new TransactionOptions {IsolationLevel = IsolationLevel.ReadCommitted};
using (var scope = new TransactionScope(TransactionScopeOption.RequiresNew, options, TransactionScopeAsyncFlowOption.Enabled))
{
    var aggregate = new ShoppingCart();
    aggregate.AddItem(SequentalGuid.NewGuid(), name: "Product 1", quantity: 3);


    var stream = new EventStream(id, aggregate.TakeUncommittedEvents());

    // Adding metadata item (key, value)
    stream.Metadata = new Dictionary<string, object>
    {
        { "RequestIP", "0.0.0.0" },
        { "User", "John Doe" }
    };

    var expectedVersion = aggregate.CommittedVersion + stream.Events.Count;
    await _store.SaveChangesAsync(aggregate.Id, expectedVersion, stream);

    scope.Complete();
}

// Usually transaction scope will be hidden somewhere in infrastructural part of code
using (var scope = new TransactionScope(TransactionScopeOption.RequiresNew, options, TransactionScopeAsyncFlowOption.Enabled))
{
    using (var repo = new SourcedRepo<ShoppingCart>(store))
    {
        // Open stream and restore aggregate from history
        var aggregate = await repo.LoadAsync(id);

        aggregate.AddItem(Guid.NewGuid(), "Product 1", 3);

        await repo.SaveChangesAsync(aggregate);
    }
    scope.Complete();
}