Want to save RSA public and private key in local drive

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.OpenSsl;
using Org.BouncyCastle.Crypto.Generators;
using Org.BouncyCastle.Crypto.Encodings;
using Org.BouncyCastle.Crypto.Engines;
using System.Xml;

namespace RSAKeyGeneration
{
    class Program
    {
        static void Main(string[] args)
        {
            // Declaring Variables //
            string SourceData;
            byte[] tmpSource;

            // Enter your Message Text //
            Console.WriteLine("Enter the Message you want to Encrypt");
            SourceData = Console.ReadLine();


            //Create a byte array from Source data
            tmpSource = ASCIIEncoding.ASCII.GetBytes(SourceData);
            Console.WriteLine();
            Console.WriteLine();
            Console.WriteLine(" Key pair is generating....Please wait for while");
            Console.WriteLine();

            //RSA key pair Generator generates the RSA kay pair based on the Random Number and the strength of key required 
            RsaKeyPairGenerator rsaKeyPairGenerator = new RsaKeyPairGenerator();
            rsaKeyPairGenerator.Init(new KeyGenerationParameters(new SecureRandom(), 2048));
            AsymmetricCipherKeyPair keyPair = rsaKeyPairGenerator.GenerateKeyPair();

            //Extracting the private key from the pair
            RsaKeyParameters privatekey = (RsaKeyParameters)keyPair.Private;
            RsaKeyParameters publickey = (RsaKeyParameters)keyPair.Public;


            //To print the public key in pem format
            TextWriter textWriter1 = new StringWriter();
            PemWriter pemWriter1 = new PemWriter(textWriter1);
            pemWriter1.WriteObject(publickey);
            pemWriter1.Writer.Flush();
            string print_publickey = textWriter1.ToString();
            Console.WriteLine("Public key is: {0}", print_publickey);
            Console.WriteLine();


            //To print the private key in pem format
            TextWriter textWriter2 = new StringWriter();
            PemWriter pemWriter2 = new PemWriter(textWriter2);
            pemWriter2.WriteObject(privatekey);
            pemWriter2.Writer.Flush();
            string print_privatekey = textWriter2.ToString();
            Console.WriteLine("Private key is: {0}", print_privatekey);
            Console.WriteLine();



            // want to save public key and private key in local file
           


        }
    }
}