c# 通过地址下载流然后保存文件到本地

        private void GetFileFromNetUrl(string url)
        {
            try
            {
                System.Net.WebRequest req = System.Net.WebRequest.Create(url);
                req.Method = "GET";
                //获得用户名密码的Base64编码  添加Authorization到HTTP头 不需要的账号密码的可以注释下面两行代码
                string code = Convert.ToBase64String(Encoding.ASCII.GetBytes(string.Format("{0}:{1}", "userName", "passWord")));
                req.Headers.Add("Authorization", "Basic " + code);
                byte[] fileBytes;
                using (WebResponse webRes = req.GetResponse())
                {
                    int length = (int)webRes.ContentLength;
                    HttpWebResponse response = webRes as HttpWebResponse;
                    Stream stream = response.GetResponseStream();

                    //读取到内存
                    MemoryStream stmMemory = new MemoryStream();
                    byte[] buffer = new byte[length];
                    int i;
                    //将字节逐个放入到Byte中
                    while ((i = stream.Read(buffer, 0, buffer.Length)) > 0)
                    {
                        stmMemory.Write(buffer, 0, i);
                    }
                    fileBytes = stmMemory.ToArray();//文件流Byte，需要文件流可直接return，不需要下面的保存代码
                    stmMemory.Close();

                    MemoryStream m = new MemoryStream(fileBytes);
                    string file = string.Format("F:\\666666666666.pdf");//可根据文件类型自定义后缀
                    FileStream fs = new FileStream(file, FileMode.OpenOrCreate);
                    m.WriteTo(fs);
                    m.Close();
                    fs.Close();
                }
            }
            catch (System.Exception ex)
            {
                throw ex;
            }
        }    

原文地址：https://www.cnblogs.com/xiaoheihei/p/10076973.html