Encrypt and decrypt using Rsa and FromXmlString on .Net Standard 2.0

RsaNetStandard.cs

public class Encryptor
    {
        public static void WriteXmlForCert(string thumbprint, string fileName)
        {
            var store = new X509Store(StoreName.My, StoreLocation.CurrentUser);
            store.Open(OpenFlags.ReadOnly);
            var certs = store.Certificates.Find(X509FindType.FindByThumbprint, thumbprint, false);
            store.Close();
            var cert = certs[0];
            var rsa = (RSA)cert.PublicKey.Key;

            var xml = rsa.ToXmlString2(false);

            File.WriteAllText(fileName, xml);
        }

        public static byte[] Encrypt(string text, string xmlFileName)
        {
            var rsa = RSA.Create();
            var xml = File.ReadAllText(xmlFileName);
            rsa.FromXmlString2(xml);

            var value = Encoding.UTF8.GetBytes(text);
            var enc = rsa.Encrypt(value, RSAEncryptionPadding.Pkcs1);

            return enc;
        }

        public static string Decrypt(string thumbprint, byte[] encrypted)
        {
            var store = new X509Store(StoreName.My, StoreLocation.LocalMachine);
            store.Open(OpenFlags.ReadOnly);
            var certs = store.Certificates.Find(X509FindType.FindByThumbprint, thumbprint, true);
            store.Close();
            var cert = certs[0];
            var privateKeyProvider = (System.Security.Cryptography.RSA)cert.PrivateKey;
            var decr = privateKeyProvider.Decrypt(encrypted, RSAEncryptionPadding.Pkcs1);

            return Encoding.UTF8.GetString(decr);
        }
    }

    public static class RsaExtensions
    {

        public static void FromXmlString2(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 = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "Exponent": parameters.Exponent = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "P": parameters.P = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "Q": parameters.Q = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "DP": parameters.DP = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "DQ": parameters.DQ = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "InverseQ": parameters.InverseQ = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "D": parameters.D = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                    }
                }
            }
            else
            {
                throw new Exception("Invalid XML RSA key.");
            }

            rsa.ImportParameters(parameters);
        }

        public static string ToXmlString2(this RSA rsa, bool includePrivateParameters)
        {
            RSAParameters parameters = rsa.ExportParameters(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>",
                  parameters.Modulus != null ? Convert.ToBase64String(parameters.Modulus) : null,
                  parameters.Exponent != null ? Convert.ToBase64String(parameters.Exponent) : null,
                  parameters.P != null ? Convert.ToBase64String(parameters.P) : null,
                  parameters.Q != null ? Convert.ToBase64String(parameters.Q) : null,
                  parameters.DP != null ? Convert.ToBase64String(parameters.DP) : null,
                  parameters.DQ != null ? Convert.ToBase64String(parameters.DQ) : null,
                  parameters.InverseQ != null ? Convert.ToBase64String(parameters.InverseQ) : null,
                  parameters.D != null ? Convert.ToBase64String(parameters.D) : null);
        }
    }

Extension methods stolen from here: dotnet/core#874
:-)