//加密
public string TripleDESEcrypt(string plainString,string key)
        {
            if(plainString.Equals(string.Empty))
            {
                return plainString;
            }
            TripleDESCryptoServiceProvider tdes=new TripleDESCryptoServiceProvider();
            PasswordDeriveBytes derive = new PasswordDeriveBytes(key,null);
            byte[] tdesIV=new byte[8];
            byte[] btaKey=derive.CryptDeriveKey("TripleDES","SHA1",0,tdesIV);
            byte[] btaCode=Encoding.Unicode.GetBytes(plainString);
            tdes.Mode = CipherMode.ECB;
            MemoryStream ms=new MemoryStream();            
            CryptoStream encStream = new CryptoStream(ms,tdes.CreateEncryptor(btaKey,tdesIV),CryptoStreamMode.Write);
            encStream.Write(btaCode, 0, btaCode.Length);
            encStream.FlushFinalBlock();
            encStream.Close();
            return System.Convert.ToBase64String(ms.ToArray());
        }

------解决方案--------------------
9楼的,你的解密程序为什么最后要用2个return呢? 请教