代码:
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方式下载文件
/// </summary>
/// <param name="url">http地址</param>
/// <param name="localfile">本地文件</param>
/// <returns></returns>
public bool Download(string url, string localfile)
{
bool flag = false;
long startPosition = 0; // 上次下载的文件起始位置
FileStream writeStream; // 写入本地文件流对象
long remoteFileLength = GetHttpLength(url);// 取得远程文件长度
System.Console.WriteLine("remoteFileLength=" + remoteFileLength);
if (remoteFileLength == 745)
{
//System.Console.WriteLine("远程文件不存在.");
return false;
}
// 判断要下载的文件夹是否存在
if (File.Exists(localfile))
{
//writeStream = File.OpenWrite(localfile); // 存在则打开要下载的文件
//startPosition = writeStream.Length; // 获取已经下载的长度
//if (startPosition >= remoteFileLength)
//{
// //System.Console.WriteLine("本地文件长度" + startPosition + "已经大于等于远程文件长度" + remoteFileLength);
// writeStream.Close();
// return false;
//}
//else
//{
// writeStream.Seek(startPosition, SeekOrigin.Current); // 本地文件写入位置定位
//}
return false;
}
else
{
writeStream = new FileStream(localfile, FileMode.Create);// 文件不保存创建一个文件
startPosition = 0;
}
try
{
HttpWebRequest myRequest = (HttpWebRequest)HttpWebRequest.Create(url);// 打开网络连接
if (startPosition > 0)
{
myRequest.AddRange((int)startPosition);// 设置Range值,与上面的writeStream.Seek用意相同,是为了定义远程文件读取位置
}
Stream readStream = myRequest.GetResponse().GetResponseStream();// 向服务器请求,获得服务器的回应数据流
byte[] btArray = new byte[512];// 定义一个字节数据,用来向readStream读取内容和向writeStream写入内容
int contentSize = readStream.Read(btArray, 0, btArray.Length);// 向远程文件读第一次
long currPostion = startPosition;
while (contentSize > 0)// 如果读取长度大于零则继续读
{
currPostion += contentSize;
int percent = (int)(currPostion * 100 / remoteFileLength);
//System.Console.WriteLine("percent=" + percent + "%");
writeStream.Write(btArray, 0, contentSize);// 写入本地文件
contentSize = readStream.Read(btArray, 0, btArray.Length);// 继续向远程文件读取
}
//关闭流
writeStream.Close();
readStream.Close();
flag = true; //返回true下载成功
}
catch (Exception)
{
writeStream.Close();
flag = false; //返回false下载失败
}
return flag;
}
// 从文件头得到远程文件的长度
private static long GetHttpLength(string url)
{
long length = 0;
try
{
HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(url);// 打开网络连接
HttpWebResponse rsp = (HttpWebResponse)req.GetResponse();
if (rsp.StatusCode == HttpStatusCode.OK)
{
length = rsp.ContentLength;// 从文件头得到远程文件的长度
}
rsp.Close();
return length;
}
catch (Exception e)
{
return length;
}
}
}
}
转载于:https://www.cnblogs.com/xsj1989/p/8918936.html