Paralllelism.cs

// Add parallelism with no extra code — just configure the blocks:
var getFolderContents = new TransformManyBlock<string, string>(
    folder => Directory.GetFileSystemEntries(folder),
    new ExecutionDataflowBlockOptions { MaxDegreeOfParallelism = 4 });

var computeMD5 = new TransformBlock<string, (string FilePath, string Hash)>(
    filePath => /* ... */,
    new ExecutionDataflowBlockOptions { MaxDegreeOfParallelism = 8 });