[System.Net]模拟Web请求编写简易单词查询客户端

demo: 我就不上传了

前言

在实际生活中，网络请求的应用极其常见，比如使用浏览器，程序中我们还要调用webservice。那么浏览器是怎么请求网络资源的呢？不用它可以自己请求不？

答案是可以的。

如果我们可以用自己的程序主动发起网络请求，那么我们可以：模拟提交数据，做一些简单网页游戏的外挂，可以刷一些帖子的访问量，可以抓取网络上的资源……

废话不我说，此文以使用Get方式对有道词典网进行请求为核心，编写了一个简单的单词查询客户端。正则表达式不太懂可以改为字符串基本操作，或者对其自己做一下基本的了解和学习。

【注：致初学都系列，一般以简单有意义的demo为例，介绍某类知识点（此文已以黑体标出）。其中API不懂的可以留言讨论。如有兴趣可以查询MSDN进行深入学习（笔者所期望的）】

效果图：

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" alt="" />

代码：

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

namespace NetCapture
{
    /// <summary>
    /// base类。以后我们可能写别的类似请求，通过继承此类，可以省下一些代码。
    /// </summary>
    public abstract class GetScraperBase
    {
        //正则表达式的匹配模式
        protected abstract string Pattern { get; }
        //如何过滤正则表达式匹配的结果
        protected abstract Dictionary<string, string> FilterMatch(Match match);
        //抓取网页上的内容
        public Dictionary<string, string> Scrape(string url, WebProxy proxy = null)
        {
                var request = WebRequest.Create(url); //创建request
                if (proxy != null)
                {
                    request.Proxy = proxy;//可能你在一些环境上不了网，得使用代理服务器
                }
                var response = request.GetResponse(); //获取response
                var stream = response.GetResponseStream();
                var responseReader = new StreamReader(stream);
                var content = responseReader.ReadToEnd(); //读取response(页面对应的html)
                var match = Regex.Match(content, Pattern, RegexOptions.IgnorePatternWhitespace); //筛选内容
                return FilterMatch(match);
        }
    }

    public class YouDaoScaper : GetScraperBase
    {
        protected override string Pattern
        {
            get
            {
                /* Target result in response:
                         <div class="trans-container">
                         <ul>
                         <li>n. 试验；检验</li>
                         <li>vt. 试验；测试</li>
                         <li>vi. 试验；测试</li>
                         <li>n. (Test)人名；(英)特斯特</li>
                        </ul>
                 *
                 * there are two groups in this pattern, first is '<li>(?<content>.+)</li>[\r\n\s]*'
                 * it's an unnamed group, it has four capture:
                 * first is '<li>n. 试验；检验</li>' and so on.
                 *
                 * another group is and named group 'content' , it has four capture, in this sampe:
                 * capture 1 is 'n. 试验；检验' and so on.
                */

                return @"<div\sclass=""trans-container"">[\r\n\s]*
<ul>[\r\n\s]*
(<li>(?<content>.+)</li>[\r\n\s]*)*
</ul>";
            }
        }

        protected override Dictionary<string, string> FilterMatch(Match match)
        {
            var dict=new Dictionary<string, string>();
            var content = "";
            var group=match.Groups["content"];
            if(group.Success)
            {
                foreach (Capture capture in group.Captures)
                {
                    content += (capture.Value + "\n");
                }
            }
            dict["content"]=content;
            return dict;
        }

        public string QueryWord(string word)
        {
            var url= "http://dict.youdao.com/search?q="+word;
            var dict = Scrape(url);
            return dict["content"];
        }
    }
}