using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

//添加命名空间
using System.Net;
using System.IO;

namespace Http_Web_Request
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        //双击"开始下载"添加Click事件
        private void button1_Click(object sender, EventArgs e)
        {
            string uri = comboBox1.Text;

            //HttpWebRequest对象实例:该类用于获取和操作HTTP请求 创建WebRequest对象
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);     

            //HttpWebResponse对象实例:该类用于获取和操作HTTP应答
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();   //获取答复

            //构造数据流、文件流对象实例
            Stream stream = null;
            FileStream filestream = null;

            try
            {
                //获取应答流赋值
                stream = response.GetResponseStream();    
                //确定应答内容的大小
                long size = response.ContentLength;       
                //定义"另存为对话框"文件类型
                saveFileDialog1.Filter = "网页文件(*.htm)|*.htm|ASP.NET文件(*.aspx)|*.aspx";

                //打开保存对话框 点击"确定"按钮执行
                if (saveFileDialog1.ShowDialog() == DialogResult.OK)
                {
                    //为文件流对象实例赋值
                    filestream = new FileStream(saveFileDialog1.FileName, FileMode.OpenOrCreate, FileAccess.Write);
                    int length = 1024;
                    byte[] Num = new byte[1025];       //构造字组
                    int i = 0;

                    while ((i = stream.Read(Num, 0, length)) > 0)  //流不为空写流
                    {
                        filestream.Write(Num, 0, i);               //写流
                    }
                }
            }
            catch (Exception msg)
            {
                MessageBox.Show(msg.Message);         //异常处理
            }
            finally
            {
                stream.Close();                       //关闭流
                filestream.Close();
            }
        }

    }
}