///<summary>
/// 进行DES解密。
///</summary>
///<param name="pToDecrypt">要解密的以Base64</param>
///<returns>已解密的字符串。</returns>
public string Decrypt(string pToDecrypt,string sKey)
{
    byte[] inputByteArray = Convert.FromBase64String(pToDecrypt);
    using(DESCryptoServiceProvider des = new DESCryptoServiceProvider())
    {
        des.Key=ASCIIEncoding.ASCII.GetBytes(sKey);
        des.IV=ASCIIEncoding.ASCII.GetBytes(sKey);
        System.IO.MemoryStream ms = new System.IO.MemoryStream();
        using(CryptoStream cs = new CryptoStream(ms,des.CreateDecryptor(),CryptoStreamMode.Write))
        {
            cs.Write(inputByteArray,0,inputByteArray.Length);
            cs.FlushFinalBlock();
            cs.Close();
        }
        string str = Encoding.UTF8.GetString(ms.ToArray());
        ms.Close();
        return str;
    }
}

private static void EncryptData(String inName, String outName, byte[] rijnKey, byte[] rijnIV)
 {    
     //Create the file streams to handle the input and output files.
     FileStream fin = new FileStream(inName, FileMode.Open, FileAccess.Read);
     FileStream fout = new FileStream(outName, FileMode.OpenOrCreate, FileAccess.Write);
     fout.SetLength(0);

     //Create variables to help with read and write.
     byte[] bin = new byte[100]; //This is intermediate storage for the encryption.
     long rdlen = 0;              //This is the total number of bytes written.
     long totlen = fin.Length;    //This is the total length of the input file.
     int len;                     //This is the number of bytes to be written at a time.

     SymmetricAlgorithm rijn = SymmetricAlgorithm.Create(); //Creates the default implementation, which is RijndaelManaged.         
     CryptoStream encStream = new CryptoStream(fout, rijn.CreateEncryptor(rijnKey, rijnIV), CryptoStreamMode.Write);

     Console.WriteLine("Encrypting...");

     //Read from the input file, then encrypt and write to the output file.
     while(rdlen < totlen)
     {
         len = fin.Read(bin, 0, 100);
         encStream.Write(bin, 0, len);
         rdlen = rdlen + len;
         Console.WriteLine("{0} bytes processed", rdlen);
     }

     encStream.Close();  
     fout.Close();
     fin.Close();                   
 }