[c#] HttpWebRequest简单实用封装应用类

   很多时候我们要用HttpWebRequest组件模拟http协议发送web请求，封装一个请求类看起来就很有必要了。要很好的封装一个这样的类，要考虑很多因素，比如通用性和异常处理，甚至还可以是继承性。当然，我下面要说的是一个静态类，继承什么的就算了，简单封装一下能用就行，呵呵，太懒了。

using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.IO;

namespace Uu102
{
    /// <summary>
    ///http协议模拟请求类
    ///主要考虑请求后的具体结果
    ///此类出自 uu102.com，请尊重原作者，转载请加上此链接
    /// </summary>
    class HttpHelper
    {
        /// <summary>
        /// 请求并发限制数目
        /// </summary>
       private static int DefaultConnectionLimit=1;
       private const string Accept = "*/*";
       private const string UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022)";
       private const string ContentType = "application/x-www-form-urlencoded";
       
        /// <summary>
        /// 发送资源请求。返回请求到的响应文本
        /// 之所以看到这么多形参，只是本人的水平很菜的体现^.^ 
        /// 注意，这个类并没有处理https加密请求
        /// </summary>
        /// <param name="url">发送请求的url地址</param>
        /// <param name="postString"></param>
        /// <param name="IsPost"></param>
        /// <param name="cookieContainer"></param>
        /// <param name="referer"></param>
        /// <param name="encoding"></param>
        /// <returns></returns>
        public static string GetHtml(string url, string postString, bool IsPost, CookieContainer cookieContainer, string referer, Encoding encoding)
        {
            string html = string.Empty;
            ServicePointManager.Expect100Continue = false;
            ServicePointManager.DefaultConnectionLimit = DefaultConnectionLimit;//设置并发连接数限制上额
            DefaultConnectionLimit++;
            if (string.IsNullOrEmpty(postString)) IsPost = false;
            HttpWebRequest httpWebRequest = null;
           
            HttpWebResponse httpWebResponse = null;
            try
            {
                httpWebRequest = (HttpWebRequest)HttpWebRequest.Create(url);//创建连接请求
                httpWebRequest.Method = IsPost ? "POST" : "GET";
                if (cookieContainer != null) httpWebRequest.CookieContainer = cookieContainer;
                httpWebRequest.AllowAutoRedirect = true;//【注意】这里有个时候在特殊情况下要设置为否，否则会造成cookie丢失
                httpWebRequest.ContentType = ContentType;
                httpWebRequest.Accept = Accept;
                httpWebRequest.UserAgent = UserAgent;
                if (!string.IsNullOrEmpty(referer)) httpWebRequest.Referer = referer;
                if (IsPost)  //如果是Post递交数据，则写入传的字符串数据
                {
                    byte[] byteRequest = Encoding.Default.GetBytes(postString);
                    httpWebRequest.ContentLength = byteRequest.Length;
                    Stream stream = httpWebRequest.GetRequestStream();
                    stream.Write(byteRequest, 0, byteRequest.Length);
                    stream.Close();
                }

                httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();//开始获取响应流
                Stream responseStream = httpWebResponse.GetResponseStream();
                StreamReader streamReader = new StreamReader(responseStream, encoding);
                html = streamReader.ReadToEnd();//注意这里是直接将所有的字节从头读到尾，也可以一行一行的控制，节省时间
                streamReader.Close();
                responseStream.Close();
                httpWebRequest.Abort();

                foreach (Cookie cookie in httpWebResponse.Cookies) //获取cookie
                {
                    cookieContainer.Add(cookie);
                }

                httpWebResponse.Close();
                //到这里为止，所有的对象都要释放掉，以免内存像滚雪球一样
                return html;
            }
            catch 
            {
                DefaultConnectionLimit--;
               //我这里就没做任何处理了，这里最好还是处理一下
                return null;
            }
            
        }
        #region 重载方法
        public static string GetHtml(string url, string postString, CookieContainer cookieContainer, string referer)
        {
            return GetHtml(url, postString, true, cookieContainer, referer, Encoding.UTF8);
        }
        public static string GetHtml(string url, string postString, CookieContainer cookieContainer)
        {
            return GetHtml(url, postString, true, cookieContainer, url, Encoding.UTF8);
        }
        public static string GetHtml(string url, CookieContainer cookieContainer, string referer)
        {
            return GetHtml(url, "", false, cookieContainer, referer, Encoding.UTF8);
        }
        public static string GetHtml(string url, CookieContainer cookieContainer)
        {
            return GetHtml(url, "", false, cookieContainer, url, Encoding.UTF8);
        }
        public static string GetHtml(string url)
        {
            return GetHtml(url, "", true, null, url, Encoding.UTF8);
        }
        #endregion
        /// <summary>
        /// 这个方法主要用来获取非文本的html响应正文
        /// </summary>
        /// <param name="url"></param>
        /// <param name="cookieContainer"></param>
        /// <returns></returns>
        public static Stream GetStream(string url,CookieContainer cookieContainer)
        {
            HttpWebRequest httpWebRequest = null;
            HttpWebResponse httpWebResponse = null;

            try
            {

                httpWebRequest = (HttpWebRequest)HttpWebRequest.Create(url);
                httpWebRequest.CookieContainer = cookieContainer;
                httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();
                Stream responseStream = httpWebResponse.GetResponseStream();
                return responseStream;
            }
            catch
            {
                if (httpWebRequest != null)
                {
                    httpWebRequest.Abort();
                } if (httpWebResponse != null)
                {
                    httpWebResponse.Close();
                }
                return null;
            }
        }

    }
}

代码太简单解释都免了吧？要强调的一点，上面的封装类还没有处理https这样的加密连接，以及返回的status和异常，如果是自己调试，最好是将try这个功能注释掉，免得看了半天都不知道哪出了问题。
以上的功能虽然能适合绝大部分请求，但是仍有一些请客不适合，比如当模拟上传文件等等的情况就不适用。

下次我们就聊聊加密请求，以及模拟上传文件的方法吧！

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