c# base64 解码/编码 sha256加密

/// <summary>
        /// sha256编码
        /// </summary>
        /// <param name="data"></param>
        /// <returns></returns>
        public string sha256(string data)
        {
            byte[] bytes = Encoding.UTF8.GetBytes(data);
            byte[] hash = SHA256Managed.Create().ComputeHash(bytes);

            StringBuilder builder = new StringBuilder();
            for (int i = 0; i < hash.Length; i++)
            {
                builder.Append(hash[i].ToString("X2"));
            }

            return builder.ToString();
        }
        ///编码
        public static string EncodeBase64(string code_type, string code)
        {
            string encode = "";
            byte[] bytes = Encoding.GetEncoding(code_type).GetBytes(code);
            try
            {
                encode = Convert.ToBase64String(bytes);
            }
            catch
            {
                encode = code;
            }
            return encode;
        }
        ///解码
        public static string DecodeBase64(string code_type, string code)
        {
            string decode = "";
            byte[] bytes = Convert.FromBase64String(code);
            try
            {
                decode = Encoding.GetEncoding(code_type).GetString(bytes);
            }
            catch
            {
                decode = code;
            }
            return decode;
        }