.net core使用RSA

RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            byte[] cipherbytes;
            rsa.FromXmlString(privatekey);
            cipherbytes = rsa.Decrypt(Convert.FromBase64String(content), false);

            return Encoding.UTF8.GetString(cipherbytes);

public static void FromXmlString(this RSA rsa, string xmlString)
        {
            RSAParameters parameters = new RSAParameters();
            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.LoadXml(xmlString);
            if (xmlDoc.DocumentElement.Name.Equals("RSAKeyValue"))
            {
                foreach (XmlNode node in xmlDoc.DocumentElement.ChildNodes)
                {
                    switch (node.Name)
                    {
                        case "Modulus": parameters.Modulus = Convert.FromBase64String(node.InnerText); break;
                        case "Exponent": parameters.Exponent = Convert.FromBase64String(node.InnerText); break;
                        case "P": parameters.P = Convert.FromBase64String(node.InnerText); break;
                        case "Q": parameters.Q = Convert.FromBase64String(node.InnerText); break;
                        case "DP": parameters.DP = Convert.FromBase64String(node.InnerText); break;
                        case "DQ": parameters.DQ = Convert.FromBase64String(node.InnerText); break;
                        case "InverseQ": parameters.InverseQ = Convert.FromBase64String(node.InnerText); break;
                        case "D": parameters.D = Convert.FromBase64String(node.InnerText); break;
                    }
                }
            }
            else
            {
                throw new Exception("Invalid XML RSA key.");
            }

            rsa.ImportParameters(parameters);
        }

        public static string ToXmlString(this RSA rsa, bool includePrivateParameters)
        {
            RSAParameters parameters = rsa.ExportParameters(includePrivateParameters);

            if (includePrivateParameters)
            {
                return string.Format("<RSAKeyValue><Modulus>{0}</Modulus><Exponent>{1}</Exponent><P>{2}</P><Q>{3}</Q><DP>{4}</DP><DQ>{5}</DQ><InverseQ>{6}</InverseQ><D>{7}</D></RSAKeyValue>",
                    Convert.ToBase64String(parameters.Modulus),
                    Convert.ToBase64String(parameters.Exponent),
                    Convert.ToBase64String(parameters.P),
                    Convert.ToBase64String(parameters.Q),
                    Convert.ToBase64String(parameters.DP),
                    Convert.ToBase64String(parameters.DQ),
                    Convert.ToBase64String(parameters.InverseQ),
                    Convert.ToBase64String(parameters.D));
            }
            return string.Format("<RSAKeyValue><Modulus>{0}</Modulus><Exponent>{1}</Exponent></RSAKeyValue>",
                    Convert.ToBase64String(parameters.Modulus),
                    Convert.ToBase64String(parameters.Exponent));
        }

var privateKeyRsaProvider = RSA.Create();
            privateKeyRsaProvider.FromXmlStringEx(privatekey);
            var r= Encoding.UTF8.GetString(privateKeyRsaProvider.Decrypt(Convert.FromBase64String(content), RSAEncryptionPadding.Pkcs1));
            return r;