正常情况下，处理https和http没有什么区别，如以下代码，显示了https://www.softlayer.com/的内容

string url = “https://www.softlayer.com/”;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
string encoding = response.ContentEncoding;
if (encoding == null || encoding.Length < 1) {
    encoding = "UTF-8"; //默认编码
}
StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding(encoding));
Console.Write(reader.ReadToEnd());
response.Close();

和http的不同就是地址由http改为了https

但是，如果你将 https://www.softlayer.com/ 改为 https://softlayer.com/，会发现一个异常
未能为 SSL/TLS 安全通道建立信任关系
怎么回事？ 用浏览器试一下，访问 https://www.softlayer.com/ 没有问题
访问 https://softlayer.com/ 会有证书问题（虽然是我们自己造成的）
这就对了，如果有证书问题，不做特殊处理，将会抛出异常
怎么处理呢？ 如果是dot net 2.0 或以上，加上一个确认函数就可以了，代码如：

ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
string url = “https://softlayer.com/”;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
string encoding = response.ContentEncoding;
if (encoding == null || encoding.Length < 1) {
    encoding = "UTF-8"; //默认编码
}
StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding(encoding));
Console.Write(reader.ReadToEnd());
response.Close();

public bool CheckValidationResult(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors) { // Always accept
    Console.WriteLine(“accept ” + certificate.GetName());
    return true; //总是接受
}

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

如果是dot net 1.1，写法略有不同

ServicePointManager.CertificatePolicy = new AcceptAllCertificatePolicy();

internal class AcceptAllCertificatePolicy : ICertificatePolicy {
    public AcceptAllCertificatePolicy() {
    }
    public bool CheckValidationResult(ServicePoint sPoint, System.Security.Cryptography.X509Certificates.X509Certificate cert, WebRequest wRequest, int certProb) {
    // Always accept
    return true;
    }
}

Related posts:

1. C# WebRequest处理Https请求之使用客户端证书
2. C# WebRequest发起Http Post请求模拟登陆并cookie处理示例