New Post: Multi part extraction

If you've got files all named properly and in the same directory, then all you need to do is use the file path Open (RarArchive.Open(string) or RarArchive.Open(FileInfo)
Otherwise use RarArchive.Open(IEnumerable<Stream>) for Streams with the Streams in order. You can use an C# iterator to feed it as it moves through the IEnumerable lazily depending on how you access it.

For more details look at the tests:
https://sharpcompress.codeplex.com/SourceControl/changeset/view/f4817f9ce4ac#SharpCompress.Test/Rar/RarArchiveTests.cs
https://sharpcompress.codeplex.com/SourceControl/changeset/view/f4817f9ce4ac#SharpCompress.Test/Rar/RarReaderTests.cs