MemoryStreamについて

MemoryStream ms = new MemoryStream();
byte[] b = new byte[5];
b[0] = 1;
b[1] = 2;
b[2] = 3;
b[3] = 4;
b[4] = 5;
ms.Write(b, 0, 5);

// DES_KEYとDES_IVは、それぞれbyte[8]
// pPasswordはbyte[]
public string Password
{
	set
	{
		Byte[] pass = System.Text.UnicodeEncoding.Unicode.GetBytes(value);

		MemoryStream mem = new MemoryStream();
		DESCryptoServiceProvider des = new DESCryptoServiceProvider();
		des.Padding = PaddingMode.PKCS7;

		ICryptoTransform transformer = des.CreateEncryptor(DES_KEY, DES_IV);
		CryptoStream crypto = new CryptoStream(mem, transformer,
 CryptoStreamMode.Write);
		crypto.Write(pass, 0, pass.Length);
		crypto.Flush();
		mem.Flush();
		mem.Seek(0, SeekOrigin.Begin);
		pPassword = mem.ToArray();
		crypto.Close();
		mem.Close();

		pPassLength = value.Length;
	}
// get省略
}

public void EncryptFile(string sInputFilename,
 string sOutputFilename, string sKey) 
{
	DESCryptoServiceProvider DES
		= new DESCryptoServiceProvider();
	FileStream fsEncrypted
		= new FileStream(sOutputFilename,
		FileMode.Create, FileAccess.Write);
	MemoryStream memEncrypted = new MemoryStream(64);
	ICryptoTransform desencrypt
		= DES.CreateEncryptor(DES_KEY, DES_IV);
	CryptoStream cryptostream
		= new CryptoStream(fsEncrypted,
		desencrypt, CryptoStreamMode.Write); 
	CryptoStream cryptomem
		= new CryptoStream(memEncrypted,
		desencrypt, CryptoStreamMode.Write); 
	byte[] pass
		= System.Text.ASCIIEncoding.ASCII.GetBytes(sKey);
	cryptostream.Write(pass, 0, pass.Length);
	cryptostream.Close();
	fsEncrypted.Close();
	cryptomem.Write(pass, 0, pass.Length);
	cryptomem.Flush();
	memEncrypted.Flush();
	memEncrypted.Seek(0, SeekOrigin.Begin);
	pPassword = memEncrypted.ToArray();
	cryptomem.Close();
	memEncrypted.Close();
}