[C#] C#发送Http请求

（1）GET

HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
request.Method = "GET";
request.UserAgent = DefaultUserAgent;

return request.GetResponse() as HttpWebResponse;

（2）POST

HttpWebRequest request = null;

//如果是发送HTTPS请求，证书验证总是返回true
if (url.StartsWith("https", StringComparison.OrdinalIgnoreCase))
{
    ServicePointManager.ServerCertificateValidationCallback = (sender, certificate, chain, errors) => true;
    request = WebRequest.Create(url) as HttpWebRequest;
    request.ProtocolVersion = HttpVersion.Version10;
}
else
{
    request = WebRequest.Create(url) as HttpWebRequest;
}

request.Method = "POST";
request.UserAgent = DefaultUserAgent; 
request.ContentType = "application/x-www-form-urlencoded";

//写post数据到请求体
StringBuilder buffer = new StringBuilder();
int i = 0;
foreach (string key in parameters.Keys)
{
    if (i > 0)
    {
        buffer.AppendFormat("&{0}={1}", key, parameters[key]);
    }
    else
    {
        buffer.AppendFormat("{0}={1}", key, parameters[key]);
    }
    i++;
}
byte[] data = requestEncoding.GetBytes(buffer.ToString());
using (Stream stream = request.GetRequestStream())
{
    stream.Write(data, 0, data.Length);
}

return request.GetResponse() as HttpWebResponse;