C#文件加密、解密问题报错

C#网上找了一个加密解密的代码，将方法引用到程序中以后，运行报错

public class DesEncrypt
    {
        private static byte[] _rgbKey = ASCIIEncoding.ASCII.GetBytes("tylgznzj");
        private static byte[] _rgbIV = ASCIIEncoding.ASCII.GetBytes("tylgidsc");
        /// 

        /// DES加密
        /// 
        /// 需要加密的值
        /// 加密后的结果
        public static string Encrypt(string text)
        {
            try
            {
                DESCryptoServiceProvider dsp = new DESCryptoServiceProvider();
                using (MemoryStream memStream = new MemoryStream())
                {
                    CryptoStream crypStream = new CryptoStream(memStream, dsp.CreateEncryptor(_rgbKey, _rgbIV), CryptoStreamMode.Write);
                    StreamWriter sWriter = new StreamWriter(crypStream);
                    sWriter.Write(text);
                    sWriter.Flush();
                    crypStream.FlushFinalBlock();
                    memStream.Flush();
                    return Convert.ToBase64String(memStream.GetBuffer(), 0, (int)memStream.Length);
                }
            }
            catch (Exception)
            {
                return null;
            }
        }
        /// 

        /// DES解密
        /// 
        /// 
        /// 解密后的结果
        public static string Decrypt(string encryptText)
        {
            try
            {
                DESCryptoServiceProvider dsp = new DESCryptoServiceProvider();
                byte[] buffer = Convert.FromBase64String(encryptText);
                using (MemoryStream memStream = new MemoryStream())
                {
                    CryptoStream crypStream = new CryptoStream(memStream, dsp.CreateDecryptor(_rgbKey, _rgbIV), CryptoStreamMode.Write);
                    crypStream.Write(buffer, 0, buffer.Length);
                    crypStream.FlushFinalBlock();
                    return ASCIIEncoding.UTF8.GetString(memStream.ToArray());
                }
            }
            catch (Exception)
            {
                return null;
            }
        }
    }

出现异常，未引用到对象

报错图片挂了，从新放一下

buf = DesEncrypt.Decrypt(reader.ReadLine());//读取解密
                //buf = reader.ReadLine();
                data = buf.Split(',');

data报错，为将对象引用到设置对象