C# RAS 非对称加密类 支持长字符串

/// <summary>
/// [e-mail]
/// </summary>
public class MyRAS
    {
        /// <summary>
        /// RAS加密
        /// </summary>
        /// <param name="xmlPublicKey">公钥</param>
        /// <param name="EncryptString">明文</param>
        /// <returns>密文</returns>

        public static string RSAEncrypt(string xmlPublicKey, string EncryptString)
        {
            byte[] PlainTextBArray;
            byte[] CypherTextBArray;
            string Result=String.Empty;
            System.Security.Cryptography.RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(xmlPublicKey);
            int t = (int)(Math.Ceiling((double)EncryptString.Length / (double)));
            //分割明文
            for (int i = ; i <= t-; i++)
            {

                PlainTextBArray = (new UnicodeEncoding()).GetBytes(EncryptString.Substring(i * , EncryptString.Length - (i * ) >  ?  : EncryptString.Length - (i * )));
                CypherTextBArray = rsa.Encrypt(PlainTextBArray, false);
                Result += Convert.ToBase64String(CypherTextBArray) + "ThisIsSplit";
            }
            return Result;
        }
        /// <summary>
        /// RAS解密
        /// </summary>
        /// <param name="xmlPrivateKey">私钥</param>
        /// <param name="DecryptString">密文</param>
        /// <returns>明文</returns>
        public static string RSADecrypt(string xmlPrivateKey, string DecryptString)
        {
            byte[] PlainTextBArray;
            byte[] DypherTextBArray;
            string Result=String.Empty;
            System.Security.Cryptography.RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(xmlPrivateKey);
            string[] Split = new string[];
            Split[] = "ThisIsSplit";
            //分割密文
            string[] mis = DecryptString.Split(Split, StringSplitOptions.RemoveEmptyEntries);
            for (int i = ; i < mis.Length; i++)
            {
                PlainTextBArray = Convert.FromBase64String(mis[i]);
                DypherTextBArray = rsa.Decrypt(PlainTextBArray, false);
                Result += (new UnicodeEncoding()).GetString(DypherTextBArray);
            }
            return Result;
        }

        /// <summary>
        /// 产生公钥和私钥对
        /// </summary>
        /// <returns>string[] 0:私钥;1:公钥</returns>
        public static string[] RSAKey()
        {
            string[] keys = new string[];
            System.Security.Cryptography.RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            keys[] = rsa.ToXmlString(true);
            keys[] = rsa.ToXmlString(false);
            return keys;
        }
    }