C# 模拟Http请求、下载

1.引入必须的命名空间：

using System.Net;
using System.IO;

2.模拟Http请求：

        /// <summary>
        /// 发送post请求
        /// </summary>
        /// <param name="Url">请求的url路径</param>
        /// <param name="postDataStr">参数</param>
        /// <returns>返回响应结果（字符串、json、xml）</returns>
        private string HttpPost(string _url, string _pms)
        {
            //创建request请求对象
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(_url);
            //请求方式
            request.Method = "POST";
            request.ContentType = "application/x-www-form-urlencoded";
            request.ContentLength = Encoding.UTF8.GetByteCount(_pms);
            Stream myRequestStream = request.GetRequestStream();
            StreamWriter myStreamWriter = new StreamWriter(myRequestStream, Encoding.GetEncoding("gb2312"));
            myStreamWriter.Write(_pms);
            myStreamWriter.Close();

            //创建response响应对象
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            Stream myResponseStream = response.GetResponseStream();
            StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.GetEncoding("utf-8"));
            string retString = myStreamReader.ReadToEnd();
            myStreamReader.Close();
            myResponseStream.Close();

            return retString;
        }

 public string HttpGet(string Url, string postDataStr)
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url + (postDataStr == "" ? "" : "?") + postDataStr);
            request.Method = "GET";
            request.ContentType = "text/html;charset=UTF-8";
 
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            Stream myResponseStream = response.GetResponseStream();
            StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.GetEncoding("utf-8"));
            string retString = myStreamReader.ReadToEnd();
            myStreamReader.Close();
            myResponseStream.Close();
 
            return retString;
        }

3.模拟http下载：

 /// <summary>
       /// 模拟http下载文件到本地
       /// </summary>
       /// <param name="_url">下载链接</param>
       /// <param name="_localPath">本地存放地址</param>
       /// <returns>本地存放路径</returns>
        public static string HttpDownloadFile(string _url, string _localPath)
        {

            if(File.Exists(_localPath)){
                return _localPath;
            }
            // 设置参数
            HttpWebRequest request = WebRequest.Create(_url) as HttpWebRequest;

            //发送请求并获取相应回应数据
            HttpWebResponse response = request.GetResponse() as HttpWebResponse;
            //直到request.GetResponse()程序才开始向目标网页发送Post请求
            Stream responseStream = response.GetResponseStream();

            //创建本地文件写入流
            Stream stream = new FileStream(_localPath, FileMode.Create);

            byte[] byteArry = new byte[1024];
            int size = responseStream.Read(byteArry, 0, (int)byteArry.Length);
            while (size > 0)
            {
                stream.Write(byteArry, 0, size);
                size = responseStream.Read(byteArry, 0, (int)byteArry.Length);
            }
            stream.Close();
            responseStream.Close();
            return _localPath;
        }