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

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        /// <summary>
        /// 更新进度条委托
        /// </summary>
        /// <param name="strValue"></param>
        delegate void UpdateInfo(int strValue);

        private void button1_Click(object sender, EventArgs e)
        {
           
            if (txtDown.Text.Trim() == String.Empty)
            {
                return;
            }

            #region 通过请求字节数获取进度条最大值

            HttpWebRequest MyReq = (HttpWebRequest)HttpWebRequest.Create(txtDown.Text.Trim());
            HttpWebResponse MyRes = (HttpWebResponse)MyReq.GetResponse();
            progressBar1.Maximum = (int)MyRes.ContentLength / 1024+1;

            #endregion
            

            #region 获取下载地址的文件名

            string[] DownUrl = txtDown.Text.Trim().Split('/');
            string cFileName = DownUrl[DownUrl.Length - 1];
            string cFileName_Remove = "";
            if (cFileName.Contains("?"))
            {
                cFileName_Remove = cFileName.Remove(cFileName.IndexOf("?"));
                saveFileDialog1.FileName = cFileName_Remove;
            }
            else
            {
                saveFileDialog1.FileName = cFileName;
            }  
 
            #endregion
            
            //打开保存对话框
            saveFileDialog1.ShowDialog();

            #region 启动下载线程

            if (saveFileDialog1.FileName != String.Empty)
            {
                Thread tUpdatelabel = new Thread(new ThreadStart(DownFile));//线程控制
                tUpdatelabel.Start();
            }

            #endregion
            
        }

        /// <summary>
        /// 下载
        /// </summary>
        private void DownFile()
        {
            HttpWebRequest MyReq = (HttpWebRequest)HttpWebRequest.Create(txtDown.Text.Trim());
            HttpWebResponse MyRes = (HttpWebResponse)MyReq.GetResponse();
            if (MyRes.ContentLength > 0)
            {
                Stream stream_Url = MyRes.GetResponseStream();
                Stream stream_FileDown = new FileStream(saveFileDialog1.FileName, FileMode.Create);
                byte[] Mybyte = new byte[1024];
                int osize = stream_Url.Read(Mybyte, 0, Mybyte.Length);
                int i=0;
                while (osize > 0)
                { 
                    i++;
                    UpdateprogressBar(i);
                    stream_FileDown.Write(Mybyte, 0, Mybyte.Length);
                    osize = stream_Url.Read(Mybyte, 0, (int)Mybyte.Length);  
                }
                stream_FileDown.Close();
                stream_Url.Close();
            }
            MessageBox.Show("下载成功！");
        }

        /// <summary>
        /// progressBar更新值变化
        /// </summary>
        /// <param name="strValue"></param>
        private void UpdateprogressBar(int strValue)
        {
            Form1 MyForm = this;
            if (MyForm.InvokeRequired)
            {
                UpdateInfo updateInfo = new UpdateInfo(UpdateprogressBar);
                MyForm.progressBar1.Invoke(updateInfo, new object[] { strValue });
            }
            else
            {
                MyForm.progressBar1.Value = strValue;
            }
        }
    }
}