DES解密，ECB模式，PKCS7填充标准

public class DesHelper
    {
        private static String _ConstValue = "12345678";
        public static String Decipher(String Str, bool IncludeLocalInfo)
        {
            if (null == Str || 0 == Str.Length) return "";
            try
            {
                SymmetricAlgorithm sa = new DESCryptoServiceProvider();
                String _Key = _ConstValue;
                sa.Key = Encoding.UTF8.GetBytes(_Key);
                sa.IV = Encoding.UTF8.GetBytes(_ConstValue);
                sa.Mode = System.Security.Cryptography.CipherMode.ECB;
                sa.Padding = PaddingMode.PKCS7;
                 ICryptoTransform ct = sa.CreateDecryptor();
                byte[] byt = Convert.FromBase64String(Str);
                MemoryStream ms = new MemoryStream();
                CryptoStream cs = new CryptoStream(ms, ct, CryptoStreamMode.Write);
                cs.Write(byt, 0, byt.Length);
                cs.FlushFinalBlock();
                cs.Close();
                return Encoding.UTF8.GetString(ms.ToArray());
            }
            catch(Exception e) {

            }
            return "";
        }
    }