public static string ToLocalhost(this string fileName)
{
// don't do this if it is done already
if (fileName.StartsWith(ServerBase.ServerUrlWithBloomPrefixEndingInSlash)) return fileName;
return ServerBase.ServerUrlWithBloomPrefixEndingInSlash + fileName.EscapeCharsForHttp().Replace(System.IO.Path.DirectorySeparatorChar, '/');
}