C＃ - X509Certificate使用私钥签名

Question

我在使用证书时遇到问题。我需要从商店中提取证书（P12），使用给定的密码检索其私钥，使用SHA1算法创建私钥的数字签名，最后将签名的签名转换为base64格式。我使用以下代码，但它完全陷入困境：

 private string GetCertificado(string strNCertif)
    {
        //Certificado RSA PKCS#12 (.P12) 

        string strPKI = string.Empty;

        X509Store stoLocalizCertif = new X509Store(StoreName.Root, StoreLocation.LocalMachine);
        stoLocalizCertif.Open(OpenFlags.ReadOnly);

        X509Certificate2Collection Resultado =
                stoLocalizCertif.Certificates.Find(X509FindType.FindByIssuerDistinguishedName, strNCertif, true);
        if (!(Resultado.Count.Equals(0)))
        {

            X509Certificate2 objCertificado = Resultado[0];

            var objChvPrv = objCertificado.PrivateKey as RSACryptoServiceProvider;
            byte[] bytCertifValor = Resultado.Export(X509ContentType.Pkcs12, "password"); //-> Key not valid for use in specified state.

            byte[] bytAssinatura = objChvPrv.SignData(bytCertifValor, new SHA1Managed());
            byte[] bytCodific = SHA1Managed.Create().ComputeHash(bytCertifValor);
            RSAPKCS1SignatureFormatter objFormata = new RSAPKCS1SignatureFormatter(objCertificado.PrivateKey);
            objFormata.SetHashAlgorithm("SHA1");
            bytAssinatura = objFormata.CreateSignature(bytCodific);

            strPKI = Convert.ToBase64String(bytAssinatura);

            stoLocalizCertif.Close();
        }
        return strPKI;
    }

有什么想法？提前谢谢。