用.NET语言写一个RSA加解密字符串的类，可以指定公钥和私钥

以下是基于.NET语言（C#）的RSA加解密字符串的类，可以指定公钥和私钥：

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

public class RSAEncryptor
{
    private RSAParameters publicKey;
    private RSAParameters privateKey;

    public RSAEncryptor(string publicKey, string privateKey)
    {
        RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
        rsa.FromXmlString(publicKey);
        this.publicKey = rsa.ExportParameters(false);

        rsa = new RSACryptoServiceProvider();
        rsa.FromXmlString(privateKey);
        this.privateKey = rsa.ExportParameters(true);
    }

    public string Encrypt(string plainText)
    {
        byte[] plainBytes = Encoding.UTF8.GetBytes(plainText);
        byte[] encryptedBytes;

        using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
        {
            rsa.ImportParameters(publicKey);
            encryptedBytes = rsa.Encrypt(plainBytes, true);
        }

        return Convert.ToBase64String(encryptedBytes);
    }

    public string Decrypt(string encryptedText)
    {
        byte[] encryptedBytes = Convert.FromBase64String(encryptedText);
        byte[] decryptedBytes;

        using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
        {
            rsa.ImportParameters(privateKey);
            decryptedBytes = rsa.Decrypt(encryptedBytes, true);
        }

        return Encoding.UTF8.GetString(decryptedBytes);
    }
}

使用示例：

string publicKey = "<RSAKeyValue><Modulus>...</Modulus><Exponent>...</Exponent></RSAKeyValue>";
string privateKey = "<RSAKeyValue><Modulus>...</Modulus><Exponent>...</Exponent><P>...</P><Q>...</Q><DP>...</DP><DQ>...</DQ><InverseQ>...</InverseQ><D>...</D></RSAKeyValue>";
RSAEncryptor encryptor = new RSAEncryptor(publicKey, privateKey);
string plainText = "Hello, world!";
string encryptedText = encryptor.Encrypt(plainText);
string decryptedText = encryptor.Decrypt(encryptedText);
Console.WriteLine(encryptedText);
Console.WriteLine(decryptedText);

请注意：在使用时，应该将实际的公钥和私钥替换为实际的值。此处给出的是XML格式的RSA密钥对，也可以使用其他格式的密钥对。