httpClient 下载

private void button2_Click(object sender, EventArgs e)
        {
            get();
        }
        private async Task get()
        {
            await DownloadFile(@"https://stg-gaminghub.omen.com/launchvideo/Oasis_30s_720p.mp4", "test.mp4");
            MessageBox.Show("finished..");
        }
        public async Task  DownloadFile(string serverFilePath, string targetPath)
        {
           await Task.Run(() =>
            {
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(serverFilePath);
                WebResponse respone = request.GetResponse();
                Stream netStream = respone.GetResponseStream();
                using (Stream fileStream = new FileStream(targetPath, FileMode.Create))
                {
                    byte[] read = new byte[1024];
                    int realReadLen = netStream.Read(read, 0, read.Length);
                    while (realReadLen > 0)
                    {
                        fileStream.Write(read, 0, realReadLen);
                        realReadLen = netStream.Read(read, 0, read.Length);
                    }
                    netStream.Close();
                    fileStream.Close();
                }
            });
          
        }
        private async void test(string serverFilePath, string targetPath)
        {
            var client = new HttpClient();
            var netStream = await client.GetStreamAsync("");
 
            using (Stream fileStream = new FileStream(targetPath, FileMode.Create))
            {
                byte[] read = new byte[1024];
                int realReadLen = netStream.Read(read, 0, read.Length);
                while (realReadLen > 0)
                {
                    fileStream.Write(read, 0, realReadLen);
                    realReadLen = netStream.Read(read, 0, read.Length);
                }
                netStream.Close();
                fileStream.Close();
            }
        }