public virtual async Task <T> GetByIdAsync <T>(Guid id) where T : AggregateRoot
{
T item = default(T);
var isSnapshottable = typeof(ISnapshottable).IsAssignableFrom(typeof(T));
Snapshot.Snapshot snapshot = null;
if ((isSnapshottable) && (SnapshotStorageProvider != null))
{
snapshot = await SnapshotStorageProvider.GetSnapshotAsync(typeof(T), id);
}
if (snapshot != null)
{
item = ReflectionHelper.CreateInstance <T>();
((ISnapshottable)item).ApplySnapshot(snapshot);
var events = await EventStorageProvider.GetEventsAsync(typeof(T), id, snapshot.Version + 1, int.MaxValue);
item.LoadsFromHistory(events);
}
else
{
var events = (await EventStorageProvider.GetEventsAsync(typeof(T), id, 0, int.MaxValue)).ToList();
if (!events.Any())
{
return(item);
}
item = ReflectionHelper.CreateInstance <T>();
item.LoadsFromHistory(events);
}
return(item);
}
private async Task CommitChanges(AggregateRoot aggregate)
{
var expectedVersion = aggregate.LastCommittedVersion;
IEvent item = await EventStorageProvider.GetLastEventAsync(aggregate.GetType(), aggregate.Id);
if ((item != null) && (expectedVersion == (int)AggregateRoot.StreamState.NoStream))
{
throw new AggregateCreationException($"Aggregate {item.CorrelationId} can't be created as it already exists with version {item.TargetVersion + 1}");
}
if ((item != null) && ((item.TargetVersion + 1) != expectedVersion))
{
throw new ConcurrencyException($"Aggregate {item.CorrelationId} has been modified externally and has an updated state. Can't commit changes.");
}
var changesToCommit = aggregate.GetUncommittedChanges().ToList();
//perform pre commit actions
foreach (var e in changesToCommit)
{
DoPreCommitTasks(e);
}
//CommitAsync events to storage provider
await EventStorageProvider.CommitChangesAsync(aggregate);
//Publish to event publisher asynchronously
foreach (var e in changesToCommit)
{
await EventPublisher.PublishAsync(e);
}
//If the Aggregate implements snaphottable
var snapshottable = aggregate as ISnapshottable;
if ((snapshottable != null) && (SnapshotStorageProvider != null))
{
//Every N events we save a snapshot
if ((aggregate.CurrentVersion >= SnapshotStorageProvider.SnapshotFrequency) &&
(
(changesToCommit.Count >= SnapshotStorageProvider.SnapshotFrequency) ||
(aggregate.CurrentVersion % SnapshotStorageProvider.SnapshotFrequency < changesToCommit.Count) ||
(aggregate.CurrentVersion % SnapshotStorageProvider.SnapshotFrequency == 0)
)
)
{
await SnapshotStorageProvider.SaveSnapshotAsync(aggregate.GetType(), snapshottable.TakeSnapshot());
}
}
aggregate.MarkChangesAsCommitted();
}
