//RSA的加密函数
public static string RSAEncrypt(string xmlPublicKey,string EncryptString )
{
byte[] PlainTextBArray;
byte[] CypherTextBArray;
string Result;
RSACryptoServiceProvider rsa=new RSACryptoServiceProvider();
UnicodeEncoding enc=new UnicodeEncoding();
xmlPublicKey=rsa.ToXmlString(false);//创建XML字符串表示形式的公钥
rsa.FromXmlString(xmlPublicKey);
PlainTextBArray =enc.GetBytes(EncryptString);
CypherTextBArray = rsa.Encrypt(PlainTextBArray, false);
//Result=(new UnicodeEncoding()).GetString(CypherTextBArray);
Result=Convert.ToBase64String(CypherTextBArray);
return  Result;
}在这里