DirectoryExtensionss.cs

using System.IO;
namespace IOExtensions
{
    public static class DirectoryExtensions
    {
        public static bool IsHidden(this DirectoryInfo dir)
        {
            return (dir.Attributes & FileAttributes.Hidden) == FileAttributes.Hidden;
        }

        public static bool IsReadonly(this DirectoryInfo dir)
        {
            return (dir.Attributes & FileAttributes.ReadOnly) == FileAttributes.ReadOnly;
        }

        public static DirectoryInfo SetHidden(this DirectoryInfo dir, bool hidden)
        {
            if (hidden)
            {
                dir.Attributes |= FileAttributes.Hidden;
            }
            else
            {
                dir.Attributes &= ~FileAttributes.Hidden;
            }
            return dir;
        }

        public static DirectoryInfo SetReadonly(this DirectoryInfo dir, bool @readonly)
        {
            if (@readonly)
            {
                dir.Attributes |= FileAttributes.ReadOnly;
            }
            else
            {
                dir.Attributes &= ~FileAttributes.ReadOnly;
            }
            return dir;
        }
    }
}

FileExtensions.cs

using System.IO;
namespace IOExtensions
{
    public static class FileExtensions
    {
        public static bool IsHidden(this FileInfo file)
        {
            return (file.Attributes & FileAttributes.Hidden) == FileAttributes.Hidden;
        }

        public static bool IsReadonly(this FileInfo file)
        {
            return (file.Attributes & FileAttributes.ReadOnly) == FileAttributes.ReadOnly;
        }

        public static FileInfo SetHidden(this FileInfo file, bool hidden)
        {
            if (hidden)
            {
                file.Attributes |= FileAttributes.Hidden;
            }
            else
            {
                file.Attributes &= ~FileAttributes.Hidden;
            }
            return file;
        }

        public static FileInfo SetReadonly(this FileInfo file, bool @readonly)
        {
            if (@readonly)
            {
                file.Attributes |= FileAttributes.ReadOnly;
            }
            else
            {
                file.Attributes &= ~FileAttributes.ReadOnly;
            }
            return file;
        }
    }
}