【C#】HTTP请求GET，POST

HTTP定义了与服务器交互的不同方法，基本方法有GET，POST，PUT，DELETE，分别对于查，该，增，删。一般情况下我们只用到GET和POST，其他两种都也可以用GET和POST来实现，很多浏览器也只实现了GET和POST两种方法

　　GET：用户获取信息

　　　　安全的：不会对服务器上的数据进行修改，和破坏

　　　　幂等的：相同的请求所返回的结果相同

　　　　参数是通过Url来传输，接在Url后面中间用?分开，不同参数之间用&分开，下面表示传递两个参数param1和param2，值为value1和value2

　　　　　　http://songurl/index.htm?param1=value1&param2=value2

　　　　通过上面可以看到，GET请求数据在隐私方面又是不安全的，因为Url上的信息可以直接让用户看到，这样不利于隐私保护

　　POST：用于更新数据

　　　　传递的数据对用户隐藏，封装在包里，具体看演示

　　　　有时候请求会重定向，但我们就需要从重定向url获取东西，这时可以设置重定向禁用，你就可以从headers的Location属性中获取重定向地址

　　　　　　request.AllowAutoRedirect = false;

　　　　　　string[] values = request.Headers.GetValues("Location");

下面是辅助类的定义

        public class HttpHelper
        {
            /// <summary>  
            /// 创建GET方式的HTTP请求  
            /// </summary>  
            public static HttpWebResponse CreateGetHttpResponse(string url, int timeout, string userAgent, CookieCollection cookies)
            {
                HttpWebRequest request = null;
                if (url.StartsWith("https", StringComparison.OrdinalIgnoreCase))
                {
                    //对服务端证书进行有效性校验（非第三方权威机构颁发的证书，如自己生成的，不进行验证，这里返回true）
                    ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
                    request = WebRequest.Create(url) as HttpWebRequest;
                    request.ProtocolVersion = HttpVersion.Version10;    //http版本，默认是1.1,这里设置为1.0
                }
                else
                {
                    request = WebRequest.Create(url) as HttpWebRequest;
                }
                request.Method = "GET";
                
                //设置代理UserAgent和超时
                //request.UserAgent = userAgent;
                //request.Timeout = timeout;
                if (cookies != null)
                {
                    request.CookieContainer = new CookieContainer();
                    request.CookieContainer.Add(cookies);
                }
                return request.GetResponse() as HttpWebResponse;
            }
            
            /// <summary>  
            /// 创建POST方式的HTTP请求  
            /// </summary>  
            public static HttpWebResponse CreatePostHttpResponse(string url, IDictionary<string, string> parameters, int timeout, string userAgent, CookieCollection cookies)
            {
                HttpWebRequest request = null;
                //如果是发送HTTPS请求  
                if (url.StartsWith("https", StringComparison.OrdinalIgnoreCase))
                {
                    //ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
                    request = WebRequest.Create(url) as HttpWebRequest;
                    //request.ProtocolVersion = HttpVersion.Version10;
                }
                else
                {
                    request = WebRequest.Create(url) as HttpWebRequest;
                }
                request.Method = "POST";
                request.ContentType = "application/x-www-form-urlencoded";

                //设置代理UserAgent和超时
                //request.UserAgent = userAgent;
                //request.Timeout = timeout; 

                if (cookies != null)
                {
                    request.CookieContainer = new CookieContainer();
                    request.CookieContainer.Add(cookies);
                }
                //发送POST数据  
                if (!(parameters == null || parameters.Count == 0))
                {
                    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 = Encoding.ASCII.GetBytes(buffer.ToString());
                    using (Stream stream = request.GetRequestStream())
                    {
                        stream.Write(data, 0, data.Length);
                    }
                }
                string[] values = request.Headers.GetValues("Content-Type");
                return request.GetResponse() as HttpWebResponse;
            }

            /// <summary>
            /// 获取请求的数据
            /// </summary>
            public static string GetResponseString(HttpWebResponse webresponse)
            {
                using (Stream s = webresponse.GetResponseStream())
                {
                    StreamReader reader = new StreamReader(s, Encoding.UTF8);
                    return reader.ReadToEnd();

                }
            }
            
            /// <summary>
            /// 验证证书
            /// </summary>
            private static bool CheckValidationResult(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors)
            {
                if (errors == SslPolicyErrors.None)
                    return true;
                return false;
            }  
        }