通过http请求获取指定url的页面

一、定义类

public class HttpWebResponseUtility
    {
        private static readonly string DefaultUserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; SV1; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";
        /// <summary>
        /// 创建GET方式的HTTP请求
        /// </summary>
        /// <param name="url">请求的URL</param>
        /// <param name="timeout">请求的超时时间</param>
        /// <param name="userAgent">请求的客户端浏览器信息，可以为空</param>
        /// <param name="cookies">随同HTTP请求发送的Cookie信息，如果不需要身份验证可以为空</param>
        /// <returns></returns>
        public static string CreateGetHttpResponse(string url,int? timeout,string userAgent=null,CookieCollection cookies=null)
        {
            if(string.IsNullOrEmpty(url))
            {
                throw new ArgumentNullException("url");
            }
            HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
            request.Method = "GET";
            request.UserAgent = DefaultUserAgent;
          
            if(!string.IsNullOrEmpty(userAgent))
            {
                request.UserAgent = userAgent;
            }
            if(timeout.HasValue)
            {
                request.Timeout = timeout.Value;
            }
            if(cookies != null)
            {
                request.CookieContainer = new CookieContainer();
                request.CookieContainer.Add(cookies);
            }

            HttpWebResponse webreponse = request.GetResponse() as HttpWebResponse;
            try
            {
                using(StreamReader reader = new StreamReader(webreponse.GetResponseStream(),System.Text.Encoding.UTF8))
                {
                    return reader.ReadToEnd();
                }
            }

            catch(Exception exp)
            {
                return exp.ToString();
            }
        }
    }