允许在C＃windows phone 8.1中验证SSL证书

Question

Windows Phone 8.1和Windows窗体中C＃之间的区别???

C＃代码在Windows窗体中运行良好！

using System.IO;
using System.Net;
using System.Net.Security;
using System.Security.Cryptography.X509Certificates;

public static string ConnectSSL(string url)
{
    url = "https://203.113.167.1/CMCSoft.IU.Web.info/login.aspx";
    WebRequest request = WebRequest.Create(url);
    request.Proxy = null;
    request.Credentials = CredentialCache.DefaultCredentials;

    //allows for validation of SSL certificates
    ServicePointManager.ServerCertificateValidationCallback += new RemoteCertificateValidationCallback(ValidateServerCertificate);
    ServicePointManager.ServerCertificateValidationCallback = ((sender, certificate, chain, sslPolicyErrors) => true);

    HttpWebResponse response = (HttpWebResponse)request.GetResponse();
    Stream dataStream = response.GetResponseStream();
    StreamReader reader = new StreamReader(dataStream);
    string responseFromServer = reader.ReadToEnd();
    return responseFromServer;
}
public static bool ValidateServerCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
{
    return true;
}

但是对于Windows Phone 8.1，缺乏使用它：

using System.Net.Security;
using System.Security.Cryptography.X509Certificates;

如何在Windows Phone 8.1上运行程序？ 感谢所有的帮助！