Can't connect to https page

[Mostafa Siraj]

Hello, I'm trying to access an https page, I don't know why .NET doesn't allow it here is the error I got "The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel." and when I try to override ServicePointManager.ServerCertificateValidationCallback with this function

public static bool ValidateServerCertificate(
object sender,
X509Certificate certificate,
X509Chain chain,
SslPolicyErrors sslPolicyErrors)
{
return true;
}

I got time out exception. here is a snippet of my code

    ServicePointManager.ServerCertificateValidationCallback += new System.Net.Security.RemoteCertificateValidationCallback(ValidateServerCertificate);
    CookieContainer c = new CookieContainer();

    reqLogin = (HttpWebRequest)WebRequest.Create(url);
    reqLogin.Method = "POST";
    reqLogin.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.3)     Gecko/2008092417 Firefox/3.0.3 (.NET CLR 3.5.30729)";
    
    reqLogin.ContentType = "application/x-www-form-urlencoded";
    reqLogin.KeepAlive = true;
    reqLogin.CookieContainer = new CookieContainer();
    reqLogin.CookieContainer = c;
    //reqLogin.CookieContainer.Add(col1);
    reqLogin.AllowAutoRedirect = true;
    reqLogin.UseDefaultCredentials = true;
    reqLogin.Timeout = 5000;                     

    using (StreamWriter sendingData = new
        StreamWriter(reqLogin.GetRequestStream()))
    {
        sendingData.Write(postMessage);
        sendingData.Flush();
        sendingData.Close();
    }

    resLogin = (HttpWebResponse)reqLogin.GetResponse();

I'm sure that you faced that problem before, i'm searching about a solution for this problem from 4 hours and couldn't find any solution, I really hope that you can help me Thanks in Advance.