//加密
byte[] enData;
private void encrypt(){
                string str = txtContent.Text;
                byte[] data = System.Text.ASCIIEncoding.ASCII.GetBytes(str);
                X509Certificate2 cert = new X509Certificate2("C:\\abc.cer");
                RSACryptoServiceProvider rsa = (RSACryptoServiceProvider)cert.PublicKey.Key;
                enData = rsa.Encrypt(data, false);//加密，得到加密后的字节组（该步骤是成功的）
}

//解密
private void decrypt(){
                X509Certificate2 cert = new X509Certificate2("C:\\abc.pfx", "123");
                RSACryptoServiceProvider rsa = (RSACryptoServiceProvider)cert.PrivateKey;
                byte[] data = rsa.Decrypt(enData, false);//解密（报错了:不正确的项）
}