GetEventStoreRepository.cs

public class GetEventStoreRepository : IRepository
{
    private const string EventClrTypeHeader = "EventClrTypeName";
    private const string AggregateClrTypeHeader = "AggregateClrTypeName";
    private const string CommitIdHeader = "CommitId";
    private const int WritePageSize = 500;
    private const int ReadPageSize = 500;

    private readonly Func<Type, Guid, string> _aggregateIdToStreamName;

    private readonly EventStoreConnection _eventStoreConnection;
    private readonly IPEndPoint _tcpEndpoint;

    public GetEventStoreRepository(EventStoreConnection eventStoreConnection, IPEndPoint eventStoreTcpEndpoint)
        : this(eventStoreConnection, eventStoreTcpEndpoint, (t, g) => string.Format("{0}-{1}", char.ToLower(t.Name[0]) + t.Name.Substring(1), g))
    {
    }

    public GetEventStoreRepository(EventStoreConnection eventStoreConnection, IPEndPoint eventStoreTcpEndpoint, Func<Type, Guid, string> aggregateIdToStreamName)
    {
        _eventStoreConnection = eventStoreConnection;
        _tcpEndpoint = eventStoreTcpEndpoint;
        _aggregateIdToStreamName = aggregateIdToStreamName;
    }

    public TAggregate GetById<TAggregate>(Guid id) where TAggregate : class, IAggregate
    {
        EnsureConnected();

        var streamName = _aggregateIdToStreamName(typeof(TAggregate), id);
        var aggregate = ConstructAggregate<TAggregate>();

        StreamEventsSlice currentSlice;
        var nextSliceStart = 1;
        do
        {
            currentSlice = _eventStoreConnection.ReadStreamEventsForward(streamName, nextSliceStart, ReadPageSize, false);
            nextSliceStart = currentSlice.NextEventNumber;

            foreach (var evnt in currentSlice.Events)
                aggregate.ApplyEvent(DeserializeEvent(evnt.OriginalEvent.Metadata, evnt.OriginalEvent.Data));
        } while (!currentSlice.IsEndOfStream);

        return aggregate;
    }

    public TAggregate GetById<TAggregate>(Guid id, int version) where TAggregate : class, IAggregate
    {
        EnsureConnected();

        var streamName = _aggregateIdToStreamName(typeof(TAggregate), id);
        var aggregate = ConstructAggregate<TAggregate>();

        var sliceStart = 1; //Ignores $StreamCreated
        StreamEventsSlice currentSlice;
        do
        {
            var sliceCount = sliceStart + ReadPageSize <= version
                                ? ReadPageSize
                                : version - sliceStart + 1;

            currentSlice = _eventStoreConnection.ReadStreamEventsForward(streamName, sliceStart, sliceCount, false);
            sliceStart = currentSlice.NextEventNumber;

            foreach (var evnt in currentSlice.Events)
                aggregate.ApplyEvent(DeserializeEvent(evnt.OriginalEvent.Metadata, evnt.OriginalEvent.Data));
        } while (version > currentSlice.NextEventNumber && !currentSlice.IsEndOfStream);

        return aggregate;
    }

    public object DeserializeEvent(byte[] metadata, byte[] data)
    {
        var eventClrTypeName = JObject.Parse(Encoding.UTF8.GetString(metadata)).Property(EventClrTypeHeader).Value;
        return JsonConvert.DeserializeObject(Encoding.UTF8.GetString(data), Type.GetType((string)eventClrTypeName));
    }

    public void Save(IAggregate aggregate, Guid commitId, Action<IDictionary<string, object>> updateHeaders)
    {
        EnsureConnected();

        var commitHeaders = new Dictionary<string, object>
            {
                {CommitIdHeader, commitId},
                {AggregateClrTypeHeader, aggregate.GetType().AssemblyQualifiedName}
            };
        updateHeaders(commitHeaders);

        var streamName = _aggregateIdToStreamName(aggregate.GetType(), aggregate.Id);
        var newEvents = aggregate.GetUncommittedEvents().Cast<object>().ToList();
        var originalVersion = aggregate.Version - newEvents.Count;
        var expectedVersion = originalVersion == 0 ? -1 : originalVersion;
        var preparedEvents = PrepareEvents(newEvents, commitHeaders).ToList();

        if (preparedEvents.Count < WritePageSize)
        {
            _eventStoreConnection.AppendToStream(streamName, expectedVersion, preparedEvents);
        }
        else
        {
            var transaction = _eventStoreConnection.StartTransaction(streamName, expectedVersion);

            var position = 0;
            while (position < preparedEvents.Count)
            {
                var pageEvents = preparedEvents.Skip(position).Take(WritePageSize);
                transaction.Write(pageEvents);
                position += WritePageSize;
            }

            transaction.Commit();
        }

        aggregate.ClearUncommittedEvents();
    }

    private static IEnumerable<EventData> PrepareEvents(IEnumerable<object> events, IDictionary<string, object> commitHeaders)
    {
        return events.Select(e => JsonEventData.Create(Guid.NewGuid(), e, commitHeaders));
    }

    private static TAggregate ConstructAggregate<TAggregate>()
    {
        return (TAggregate)Activator.CreateInstance(typeof(TAggregate), true);
    }

    private bool _isConnected;

    private void EnsureConnected()
    {
        if (_isConnected)
            return;

        _eventStoreConnection.Connect(_tcpEndpoint);
        _isConnected = true;
    }

    private static class JsonEventData
    {
        public static EventData Create(Guid eventId, object evnt, IDictionary<string, object> headers)
        {
            var data = Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(evnt, SerializerSettings));
            var metadata = AddEventClrTypeHeaderAndSerializeMetadata(evnt, headers);
            var typeName = evnt.GetType().Name;

            return new EventData(eventId, typeName, true, data, metadata);
        }

        private static readonly JsonSerializerSettings SerializerSettings;
        
        private static byte[] AddEventClrTypeHeaderAndSerializeMetadata(object evnt, IDictionary<string, object> headers)
        {
            var eventHeaders = new Dictionary<string, object>(headers)
                {
                    {EventClrTypeHeader, evnt.GetType().AssemblyQualifiedName}
                };

            return Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(eventHeaders, SerializerSettings));
        }

        static JsonEventData()
        {
            SerializerSettings = new JsonSerializerSettings { TypeNameHandling = TypeNameHandling.None };
        }
    }
}

GetEventStoreRepositoryTests.cs

/// <summary>
/// Integration tests for the GetEventStoreRepository. These tests require a
/// running version of the Event Store, with a TCP endpoint as specified in the
/// IntegrationTestTcpEndPoint field (defaults to local loopback, port 1113).
/// </summary>
[TestFixture]
public class GetEventStoreRepositoryIntegrationTests
{
    /// <summary>
    /// Set this to the TCP endpoint on which the Event Store is running.
    /// </summary>
    private static readonly IPEndPoint IntegrationTestTcpEndPoint = new IPEndPoint(IPAddress.Loopback, 1113);

    private static Guid SaveTestAggregateWithoutCustomHeaders(IRepository repository, int numberOfEvents)
    {
        var aggregateToSave = new TestAggregate(Guid.NewGuid());
        aggregateToSave.ProduceEvents(numberOfEvents);
        repository.Save(aggregateToSave, Guid.NewGuid(), d => { });
        return aggregateToSave.Id;
    }

    [Test]
    public void ClearsEventsFromAggregateOnceCommitted()
    {
        var connection = EventStoreConnection.Create();
        var repo = new GetEventStoreRepository(connection, IntegrationTestTcpEndPoint);

        var aggregateToSave = new TestAggregate(Guid.NewGuid());
        aggregateToSave.ProduceEvents(10);
        repo.Save(aggregateToSave, Guid.NewGuid(), d => { });

        Assert.AreEqual(0, ((IAggregate)aggregateToSave).GetUncommittedEvents().Count);
    }

    [Test]
    public void CanGetLatestVersionById()
    {
        var connection = EventStoreConnection.Create();
        var repo = new GetEventStoreRepository(connection, IntegrationTestTcpEndPoint);

        var savedId = SaveTestAggregateWithoutCustomHeaders(repo, 3000 /* excludes TestAggregateCreated */);

        var retrieved = repo.GetById<TestAggregate>(savedId);
        Assert.AreEqual(3000, retrieved.AppliedEventCount);

        connection.Close();
    }

    [Test]
    public void CanGetSpecificVersionFromFirstPageById()
    {
        var connection = EventStoreConnection.Create();
        var repo = new GetEventStoreRepository(connection, IntegrationTestTcpEndPoint);

        var savedId = SaveTestAggregateWithoutCustomHeaders(repo, 100  /* excludes TestAggregateCreated */);

        var retrieved = repo.GetById<TestAggregate>(savedId, 65);
        Assert.AreEqual(64, retrieved.AppliedEventCount);

        connection.Close();
    }

    [Test]
    public void CanGetSpecificVersionFromSubsequentPageById()
    {
        var connection = EventStoreConnection.Create();
        var repo = new GetEventStoreRepository(connection, IntegrationTestTcpEndPoint);

        var savedId = SaveTestAggregateWithoutCustomHeaders(repo, 500 /* excludes TestAggregateCreated */);

        var retrieved = repo.GetById<TestAggregate>(savedId, 126);
        Assert.AreEqual(125, retrieved.AppliedEventCount);

        connection.Close();
    }

    [Test]
    public void CanSaveExistingAggregate()
    {
        var connection = EventStoreConnection.Create();
        var repo = new GetEventStoreRepository(connection, IntegrationTestTcpEndPoint);

        var savedId = SaveTestAggregateWithoutCustomHeaders(repo, 100 /* excludes TestAggregateCreated */);

        var firstSaved = repo.GetById<TestAggregate>(savedId);
        firstSaved.ProduceEvents(50);
        repo.Save(firstSaved, Guid.NewGuid(), d => { });

        var secondSaved = repo.GetById<TestAggregate>(savedId);
        Assert.AreEqual(150, secondSaved.AppliedEventCount);

        connection.Close();
    }

    [Test]
    public void CanSaveMultiplesOfWritePageSize()
    {
        var connection = EventStoreConnection.Create();
        var repo = new GetEventStoreRepository(connection, IntegrationTestTcpEndPoint);

        var savedId = SaveTestAggregateWithoutCustomHeaders(repo, 1500 /* excludes TestAggregateCreated */);
        var saved = repo.GetById<TestAggregate>(savedId);

        Assert.AreEqual(1500, saved.AppliedEventCount);

        connection.Close();
    }

    [Test]
    public void GetsEventsFromCorrectStreams()
    {
        var connection = EventStoreConnection.Create();
        var repo = new GetEventStoreRepository(connection, IntegrationTestTcpEndPoint);

        var aggregate1Id = SaveTestAggregateWithoutCustomHeaders(repo, 100);
        var aggregate2Id = SaveTestAggregateWithoutCustomHeaders(repo, 50);

        var firstSaved = repo.GetById<TestAggregate>(aggregate1Id);
        Assert.AreEqual(100, firstSaved.AppliedEventCount);

        var secondSaved = repo.GetById<TestAggregate>(aggregate2Id);
        Assert.AreEqual(50, secondSaved.AppliedEventCount);

        connection.Close();
    }

    [Test]
    public void CanHandleLargeNumberOfEventsInOneTransaction()
    {
        const int numberOfEvents = 50000;

        var connection = EventStoreConnection.Create();
        var repo = new GetEventStoreRepository(connection, IntegrationTestTcpEndPoint);

        var aggregateId = SaveTestAggregateWithoutCustomHeaders(repo, numberOfEvents);

        var saved = repo.GetById<TestAggregate>(aggregateId);
        Assert.AreEqual(numberOfEvents, saved.AppliedEventCount);

        connection.Close();
    }

    [Test]
    public void SavesCommitHeadersOnEachEvent()
    {
        var connection = EventStoreConnection.Create();
        var repo = new GetEventStoreRepository(connection, IntegrationTestTcpEndPoint);

        var commitId = Guid.NewGuid();
        var aggregateToSave = new TestAggregate(Guid.NewGuid());
        aggregateToSave.ProduceEvents(20);
        repo.Save(aggregateToSave, commitId, d =>
        {
            d.Add("CustomHeader1", "CustomValue1");
            d.Add("CustomHeader2", "CustomValue2");
        });

        var read = connection.ReadStreamEventsForward(string.Format("aggregate-{0}", aggregateToSave.Id), 1, 20, false);
        foreach (var serializedEvent in read.Events)
        {
            var parsedMetadata = JObject.Parse(Encoding.UTF8.GetString(serializedEvent.OriginalEvent.Metadata));
            var deserializedCommitId = parsedMetadata.Property("CommitId").Value.ToObject<Guid>();
            Assert.AreEqual(commitId, deserializedCommitId);

            var deserializedCustomHeader1 = parsedMetadata.Property("CustomHeader1").Value.ToObject<string>();
            Assert.AreEqual("CustomValue1", deserializedCustomHeader1);

            var deserializedCustomHeader2 = parsedMetadata.Property("CustomHeader2").Value.ToObject<string>();
            Assert.AreEqual("CustomValue2", deserializedCustomHeader2);
        }

        connection.Close();
    }
}

TestAggregate.cs

public class TestAggregate : AggregateBase
{
    public int AppliedEventCount { get; private set; }

    public TestAggregate(Guid aggregateId)
        : this()
    {
        RaiseEvent(new TestAggregateCreated(aggregateId));
    }

    public void ProduceEvents(int count)
    {
        for (var i = 0; i < count; i++)
            RaiseEvent(new WoftamEvent("Woftam1-" + i, "Woftam2-" + i));
    }

    private TestAggregate()
    {
        Register<TestAggregateCreated>(e => Id = e.AggregateId);
        Register<WoftamEvent>(e => AppliedEventCount++);
    }
}

TestAggregateCreated.cs

public class TestAggregateCreated
{
    public TestAggregateCreated(Guid aggregateId)
    {
        AggregateId = aggregateId;
    }

    public Guid AggregateId { get; private set; }
}

WoftamEvent.cs

public class WoftamEvent
{
    public WoftamEvent(string property1, string property2)
    {
        Property1 = property1;
        Property2 = property2;
    }

    public string Property1 { get; private set; }
    public string Property2 { get; private set; }
}