byte[] certifContent = System.IO.File.ReadAllBytes(@"c:\...\mycertif.cer");
using (System.Security.Cryptography.X509Certificates.X509Certificate2 certif = new X509Certificate2(certifContent))
{
    string c_memo = "Le contenu du mémo qui doit être crypté.";
    using (SqlCommand cmd = new SqlCommand("update CLI set c_memo=@c_memo where c_id='AGK'"))
    {
        cmd.Parameters.AddWithValue("@c_memo", MercatorCryptorEngine.CryptorEngine.MercatorEncryptRsaAes(c_memo, certificate: certif)).SqlDbType = System.Data.SqlDbType.VarChar;
        bool b = Api.SqlExec(@"K:\MercatorDev\Data\", cmd);
    }
}