public class RSATool
  {
    public string Encrypt(string strText, string strPublicKey)
    {
      RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
      rsa.FromXmlString(strPublicKey);
      byte[] byteText = Encoding.UTF8.GetBytes(strText);
      byte[] byteEntry = rsa.Encrypt(byteText, false);
      return Convert.ToBase64String(byteEntry);
    }
    public string Decrypt(string strEntryText,string strPrivateKey)
    {
      RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
      rsa.FromXmlString(strPrivateKey);
      byte[] byteEntry = Convert.FromBase64String(strEntryText);
      byte[] byteText = rsa.Decrypt(byteEntry, false);
      return Encoding.UTF8.GetString(byteText);
    }
    public Dictionary<string,string> GetKey()
    {
      Dictionary<string, string> dictKey = new Dictionary<string, string>();
      RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
      dictKey.Add("PublicKey", rsa.ToXmlString(false));
      dictKey.Add("PrivateKey", rsa.ToXmlString(true));
      return dictKey;
    }
  }

RSATool myRSA = new RSATool();
      Dictionary<string, string> dictK = new Dictionary<string, string>();
      dictK = myRSA.GetKey();
      string strText = "123456";
      Console.WriteLine("要加密的字符串是：{0}", strText);
      string str1 = myRSA.Encrypt("123456", dictK["PublicKey"]);
      Console.WriteLine("加密后的字符串：{0}", str1);
      string str2 = myRSA.Decrypt(str1, dictK["PrivateKey"]);
      Console.WriteLine("解密后的字符串：{0}", str2);

 public class RSAToolX
  {
    public string Encrypt(string strText)
    {
      CspParameters CSApars = new CspParameters();
      CSApars.KeyContainerName = "Test001";
      RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(CSApars);
      byte[] byteText = Encoding.UTF8.GetBytes(strText);
      byte[] byteEntry = rsa.Encrypt(byteText, false);
      return Convert.ToBase64String(byteEntry);
    }
    public string Decrypt(string strEntryText)
    {
      CspParameters CSApars = new CspParameters();
      CSApars.KeyContainerName = "Test001";
      RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(CSApars);
      byte[] byteEntry = Convert.FromBase64String(strEntryText);
      byte[] byteText = rsa.Decrypt(byteEntry, false);
      return Encoding.UTF8.GetString(byteText);
    }
  }

RSAToolX myRSA = new RSAToolX();
      string strText = "123456";
      Console.WriteLine("要加密的字符串是：{0}", strText);
      string str1 = myRSA.Encrypt("123456");
      Console.WriteLine("加密后的字符串：{0}", str1);
      string str2 = myRSA.Decrypt(str1);
      Console.WriteLine("解密后的字符串：{0}", str2);