NServiceBusCommitDispatcher

gistfile1.cs

public sealed class NServiceBusCommitDispatcher : IPublishMessages
{
	private const string AggregateIdKey = "AggregateId";
	private const string CommitVersionKey = "CommitVersion";
	private const string EventVersionKey = "EventVersion";
	private const string BusPrefixKey = "Bus.";
	private readonly IBus bus;

	public NServiceBusCommitDispatcher(IBus bus)
	{
		this.bus = bus;
	}

	public void Dispose()
	{
		GC.SuppressFinalize(this);
	}

	public void Publish(Commit commit)
	{
		for (var i = 0; i < commit.Events.Count; i++)
		{
			var eventMessage = commit.Events[i];
			var busMessage = eventMessage.Body as IMessage;
			AppendHeaders(busMessage, commit.Headers);
			AppendHeaders(busMessage, eventMessage.Headers);
			AppendVersion(commit, i);
			this.bus.Publish(busMessage);
		}
	}
	private static void AppendHeaders(IMessage message, IEnumerable<KeyValuePair<string, object>> headers)
	{
		headers = headers.Where(x => x.Key.StartsWith(BusPrefixKey));
		foreach (var header in headers)
		{
			var key = header.Key.Substring(BusPrefixKey.Length);
			var value = (header.Value ?? string.Empty).ToString();
			message.SetHeader(key, value);
		}
	}
	private static void AppendVersion(Commit commit, int index)
	{
		var busMessage = commit.Events[index].Body as IMessage;
		busMessage.SetHeader(AggregateIdKey, commit.StreamId.ToString());
		busMessage.SetHeader(CommitVersionKey, commit.StreamRevision.ToString());
		busMessage.SetHeader(EventVersionKey, GetSpecificEventVersion(commit, index).ToString());
	}
	private static int GetSpecificEventVersion(Commit commit, int index)
	{
		// e.g. (StreamRevision: 120) - (5 events) + 1 + (index @ 4: the last index) = event version: 120
		return commit.StreamRevision - commit.Events.Count + 1 + index;
	}
}