数字证书加密,该如何解决

数字证书加密
我是用数字证书做的加、解密方法，我正确的生成了一个 abc.cer文件和abc.pfx文件（并设定密码123）

C# code

//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）}

C# code

//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）}