Find public key from certificate as a xml string - windows-phone-7

Question

i need to find the public key from certificate as xml string. I can take the public key only as a string with this method:
public string CelesiPublik()
{
X509Certificate cer;
cer = X509Certificate.CreateFromCertFile("C://certificate//EdonBajrami.crt");
string Celesi = cer.GetPublicKeyString();
return Celesi;
}
and then i take this value to the another method. Celesi value now has take celesiPublik
celesiPublik = e.Result;
string NrTelefonit = "044-419-109";
string salt = "VotimiElektronikKosove";
AesManaged aes = new AesManaged();
Rfc2898DeriveBytes rfc2898 = new Rfc2898DeriveBytes(celesiPublik,Encoding.UTF8.GetBytes(salt));
aes.Key = rfc2898.GetBytes(aes.KeySize / 8);
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
rsa.FromXmlString(celesiPublik);
rsa.Encrypt(aes.Key, false);
but it shows me error. How can i resolve this problem?
GregS i cannot use in Windows Phone 7 X509Certificate2. I take my public key with the method:
`X509Certificate cer = new X509Certificate("C://certificate//EdonBajrami.crt");
string publicKey = cer.GetPublicKeyString();`
i can take the public key. Then in another method i take value of the publicKey to another string variable Key:
`string Key = publicKey;
//-----First------
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
//----------
RSAParameters RSAKeyInfo = new RSAParameters();
byte[] celesibyte = System.Text.Encoding.UTF8.GetBytes(celesiPublik);
byte[] Exponent = { 1, 0, 1 };
RSAKeyInfo.Modulus = celesibyte;
RSAKeyInfo.Exponent = Exponent;
rsa.ImportParameters(RSAKeyInfo);
//-----------
/* rsa.FromXmlString(celesi2Publik); */
string edon = "Edon";
byte[] edon1 = Encoding.UTF8.GetBytes(edon);
byte[] edon2 = rsa.Encrypt(edon1, false);'
but it sends me data that is 506 byte, i dont understand why, what is a problem ?

Answer 1

As far as I can tell the X509Certificate class is nearly useless. Perhaps that is why there is a class X509Certificate2? Use the X509Certificate2 class. You can create an RSACryptoServiceProvider directly from the public key like the following:
X509Certificate2 cert = new X509Certificate2(X509Certificate.CreateFromCertFile("C://certificate//EdonBajrami.crt"));
RSACryptoServiceProvider rsa = (RSACryptoServiceProvider) cert.PublicKey.Key;