using System;

using System.Security.Cryptography; 

using System.Text;

public class Program

    {

        public static string Encrypt(string publicKeyXML, string input, int keySize , bool fOAEP)

        {

            using (var rsa = new RSACryptoServiceProvider(keySize))

            {

                rsa.FromXmlString(publicKeyXML);

                var inputBytes = Encoding.UTF8.GetBytes(input);

                var encrypted = rsa.Encrypt(inputBytes, fOAEP);

                //return Encoding.UTF8.GetString(encrypted);

                return Convert.ToBase64String(encrypted);

            }

        }

​

        public static void Main()

        {

            var publicKey="<RSAKeyValue><Modulus>jX2jfYW6vJFLXD5q0HPWcdzLA3gDxK6Iv0mw0juRm5kd9wf9AwFZ+XeLo7NDGp800NrnrybdtMmooeTST6eVoyojtZT+Bod5BIgY8Sn+9Awh8gBPP+jWyxNmCcLaLJGyvCh2TuLoqGoRScKLvzT0mPub7Sch63tAG8c4wG01mCzlYfa3gUs1YJJf2XkmyPHd5GwEsDus0s6Iw+uhRE9EAa7te2GUYIzo6z6/CCaoeom/f+WSS4xfOSJtw3ImepBZRGsThopuoKxdOFrkfCFfjr5Cr7CMunNR9OQ6gwghS79J4ROxCeH2mfj/Z1XIo+nWUE98fGPjq/xFK6d2vSQccw==</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>";

            Console.WriteLine(Encrypt(publicKey,"Bb123456",2048,true));

        }

}