RSACryptography, a set of RSA de/encryt methods who can read the p12 file with a password , and can generate public key in terms of its private key. It was written by C#.

RSACryptography.cs

//This file is encrypt/decrypt data in a default way which can not decrypt/decrypt a chunk of data

using System;
using System.Text;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;

namespace RSA_CSharp_Example
{
    class Program
    {
        static void Main(string[] args)
        {
            //Generate public key in terms of private key file
            X509Certificate2 x509 = new X509Certificate2("C:\\Users\\victor\\Desktop\\private_key.p12", "123456");

            //Gain private key
            RSACryptoServiceProvider provider = (RSACryptoServiceProvider)x509.PrivateKey;
            string public_key = x509.PublicKey.Key.ToXmlString(false);

            string hello = "hello, world!";
            string cipherHello = RSAEncrypt(public_key, hello);
            Console.WriteLine(cipherHello);
             
            string plainHello = RSADecrypt(provider, cipherHello);
            Console.WriteLine(plainHello);


            Console.ReadKey();
        }

        /// <summary>
        /// RSA Encryption
        /// </summary>
        public static string RSAEncrypt(string xmlPublicKey, string m_strEncryptString)
        {
            string result = "";
            try
            {
                RSACryptoServiceProvider provider = new RSACryptoServiceProvider();
                provider.FromXmlString(xmlPublicKey);
                byte[] bytes = new UnicodeEncoding().GetBytes(m_strEncryptString);
                result = Convert.ToBase64String(provider.Encrypt(bytes, false));
            }
            catch (Exception exception)
            {
                throw exception;
            }
            return result;
        }

        /// <summary>
        /// RSA Decryption
        /// </summary>
        public static string RSADecrypt(RSACryptoServiceProvider provider, string m_strDecryptString)
        {
            string result = "";
            try
            {
                byte[] rgb = Convert.FromBase64String(m_strDecryptString);
                byte[] buffer2 = provider.Decrypt(rgb, false);
                result = new UnicodeEncoding().GetString(buffer2);
            }
            catch (Exception exception)
            {
                throw exception;
            }
            return result;
        }
    }
}

RSACryptography1.cs

//This file is encrypt/decrypt data in a subsection way which can decrypt/decrypt a chunk of data

using System;
using System.Text;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.IO;

namespace RSA_CSharp_Example
{
    class Program
    {
        static void Main(string[] args)
        {
            //Generate public key in terms of private key file
            X509Certificate2 x509 = new X509Certificate2("C:\\Users\\victor\\Desktop\\VL_Private_Key.p12", "123456");

            //Gain private key
            RSACryptoServiceProvider provider = (RSACryptoServiceProvider)x509.PrivateKey;
            string public_key = x509.PublicKey.Key.ToXmlString(false);

            string hello = "hello my world";
            string cipherHello = RSAEncrypt(public_key, hello);
            Console.WriteLine(cipherHello);

            string plainHello = RSADecrypt(provider, cipherHello);
            Console.WriteLine(plainHello);


            Console.ReadKey();
        }

        /// <summary>
        /// RSA Encryption
        /// </summary>
        public static string RSAEncrypt(string xmlPublicKey, string m_strEncryptString)
        {
            string result = "";
            try
            {
                RSACryptoServiceProvider provider = new RSACryptoServiceProvider();
                provider.FromXmlString(xmlPublicKey);

                //https://dotblogs.com.tw/yc421206/archive/2012/06/26/73044.aspx
                //分段加密, 如果不分段加密，则会提示异常“ 要解密的数据超过此模块的最大值 128 字节”
                int bufferSize = (provider.KeySize / 8) - 11;
                byte[] buffer = new byte[bufferSize];

                //byte[] originalData = new UnicodeEncoding().GetBytes(m_strEncryptString);
                byte[] originalData = Encoding.UTF8.GetBytes(m_strEncryptString);
                MemoryStream input = new MemoryStream(originalData);
                MemoryStream output = new MemoryStream();
                int readLine = input.Read(buffer, 0, bufferSize);
                while (readLine > 0)
                {
                    if (readLine <= 0)  break; 

                    byte[] temp = new byte[readLine];
                    Array.Copy(buffer, 0, temp, 0, readLine);
                    byte[] encrypt = provider.Encrypt(temp, false);
                    output.Write(encrypt, 0, encrypt.Length);

                    readLine = input.Read(buffer, 0, bufferSize);
                }
                input.Close();
                byte[] encryptedBytes = output.ToArray();
                output.Close();
                result = Convert.ToBase64String(encryptedBytes);
                
            }
            catch (Exception exception)
            {
                throw exception;
            }
            return result;
        }
        

        /// <summary>
        /// RSA Decryption
        /// </summary>
        public static string RSADecrypt(RSACryptoServiceProvider provider, string m_strDecryptString)
        {
            string result = "";
            try
            {
                int keySize = provider.KeySize / 8; byte[] buffer = new byte[keySize];
                byte[] EncryptDada = Convert.FromBase64String(m_strDecryptString);

                using (MemoryStream input = new MemoryStream(EncryptDada))
                {
                    using (MemoryStream output = new MemoryStream())
                    {
                        while (true)
                        {
                            int readLine = input.Read(buffer, 0, keySize);
                            if (readLine <= 0)
                            {
                                break;
                            }
                            byte[] temp = new byte[readLine];
                            Array.Copy(buffer, 0, temp, 0, readLine);
                            byte[] decrypt = provider.Decrypt(temp, false);
                            output.Write(decrypt, 0, decrypt.Length);
                        }
                        result = Encoding.UTF8.GetString(output.ToArray());
                        //result = new UnicodeEncoding().GetString(buffer2);
                    }
                }
            }
            catch (Exception exception)
            {
                throw exception;
            }
            return result;
        }
         
    }
}