Upload directory to blob storage

UploadDirectoryToBlobStorage.cs

public void UploadDirectoryToBlobStorage(String directory, CloudBlobDirectory virtualDirectory = null)
{
    var directoryInfo = new DirectoryInfo(directory);

    var blobReferenceBuilder = (virtualDirectory == null) ? 
        (Func<String, CloudBlockBlob>) (n => _container.GetBlockBlobReference(n)) :
        (Func<String, CloudBlockBlob>) (n => virtualDirectory.GetBlockBlobReference(n));

    var files = directoryInfo.GetFiles();
    Array.ForEach(files, f => 
    {
        var name = Path.GetFileName(f.FullName);
        var extension = Path.GetExtension(f.FullName).Substring(1).ToLower();

        var blob = blobReferenceBuilder(name);
        if (ContentTypeMapping.ContainsKey(extension))
            blob.Properties.ContentType = ContentTypeMapping[extension];
                
        using (var stream = new MemoryStream(File.ReadAllBytes(f.FullName)))
        {
            stream.Seek(0, SeekOrigin.Begin);
            blob.UploadFromStream(stream);
            stream.Close();
        }
    });

    var directoryReferenceBuilder = (virtualDirectory == null) ? 
        (Func<String, CloudBlobDirectory>) (n => _container.GetDirectoryReference(n)) :
        (Func<String, CloudBlobDirectory>)(n => virtualDirectory.GetSubdirectoryReference(n));

    var directories = directoryInfo.GetDirectories();
    Array.ForEach(directories, d => 
    {
        var subDirectory=  directoryReferenceBuilder(d.Name);
        UploadDirectoryToBlobStorage(d.FullName, subDirectory);
    });
}