public string GetPath(byte[] contentIdentifier)
{
if (contentIdentifier == null) throw new NullReferenceException("contentIdentifier cannot be null.");
System.Text.StringBuilder sb = new System.Text.StringBuilder();
sb.Append(contentIdentifier[0].ToString("x2"));
sb.Append(Path.DirectorySeparatorChar);
sb.Append(contentIdentifier[1].ToString("x2"));
sb.Append(Path.DirectorySeparatorChar);
for(int i = 2; i < contentIdentifier.Length; i++)
sb.Append(contentIdentifier[i].ToString("x2"));
return Path.Combine(path, sb.ToString());
}