Http方式下載下傳檔案

代碼：

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Threading.Tasks;

namespace WebSiteTest.Common
{
    public class HttpDldFile
    {
        /// <summary>
        /// Http方式下載下傳檔案
        /// </summary>
        /// <param name="url">http位址</param>
        /// <param name="localfile">本地檔案</param>
        /// <returns></returns>
        public bool Download(string url, string localfile)
        {
            bool flag = false;
            long startPosition = 0; // 上次下載下傳的檔案起始位置
            FileStream writeStream; // 寫入本地檔案流對象

            long remoteFileLength = GetHttpLength(url);// 取得遠端檔案長度
            System.Console.WriteLine("remoteFileLength=" + remoteFileLength);
            if (remoteFileLength == 745)
            {
                //System.Console.WriteLine("遠端檔案不存在.");
                return false;
            }

            // 判斷要下載下傳的檔案夾是否存在
            if (File.Exists(localfile))
            {
                //writeStream = File.OpenWrite(localfile);             // 存在則打開要下載下傳的檔案
                //startPosition = writeStream.Length;                  // 擷取已經下載下傳的長度

                //if (startPosition >= remoteFileLength)
                //{
                //    //System.Console.WriteLine("本地檔案長度" + startPosition + "已經大于等于遠端檔案長度" + remoteFileLength);
                //    writeStream.Close();
                //    return false;
                //}
                //else
                //{
                //    writeStream.Seek(startPosition, SeekOrigin.Current); // 本地檔案寫入位置定位
                //}

                return false;
            }
            else
            {
                writeStream = new FileStream(localfile, FileMode.Create);// 檔案不儲存建立一個檔案
                startPosition = 0;
            }


            try
            {
                HttpWebRequest myRequest = (HttpWebRequest)HttpWebRequest.Create(url);// 打開網絡連接配接

                if (startPosition > 0)
                {
                    myRequest.AddRange((int)startPosition);// 設定Range值,與上面的writeStream.Seek用意相同,是為了定義遠端檔案讀取位置
                }


                Stream readStream = myRequest.GetResponse().GetResponseStream();// 向伺服器請求,獲得伺服器的回應資料流


                byte[] btArray = new byte[512];// 定義一個位元組資料,用來向readStream讀取内容和向writeStream寫入内容
                int contentSize = readStream.Read(btArray, 0, btArray.Length);// 向遠端檔案讀第一次

                long currPostion = startPosition;

                while (contentSize > 0)// 如果讀取長度大于零則繼續讀
                {
                    currPostion += contentSize;
                    int percent = (int)(currPostion * 100 / remoteFileLength);
                    //System.Console.WriteLine("percent=" + percent + "%");

                    writeStream.Write(btArray, 0, contentSize);// 寫入本地檔案
                    contentSize = readStream.Read(btArray, 0, btArray.Length);// 繼續向遠端檔案讀取
                }

                //關閉流
                writeStream.Close();
                readStream.Close();

                flag = true;        //傳回true下載下傳成功
            }
            catch (Exception)
            {
                writeStream.Close();
                flag = false;       //傳回false下載下傳失敗
            }

            return flag;
        }

        // 從檔案頭得到遠端檔案的長度
        private static long GetHttpLength(string url)
        {
            long length = 0;

            try
            {
                HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(url);// 打開網絡連接配接
                HttpWebResponse rsp = (HttpWebResponse)req.GetResponse();

                if (rsp.StatusCode == HttpStatusCode.OK)
                {
                    length = rsp.ContentLength;// 從檔案頭得到遠端檔案的長度
                }

                rsp.Close();
                return length;
            }
            catch (Exception e)
            {
                return length;
            }

        }
    }
}      

轉載于:https://www.cnblogs.com/xsj1989/p/8918936.html