C#-HttpClient 下载文件

HttpClient-download-file.cs

using System;
using System.Configuration;
using System.Diagnostics;
using System.IO;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace SevenStarCollect.Update
{
    public partial class MainForm : Form
    {
        private static string _address = ConfigurationManager.AppSettings["address"];

        private readonly SynchronizationContext synchronizationContext;

        private long _fileSize;

        public MainForm()
        {
            InitializeComponent();

            synchronizationContext = SynchronizationContext.Current;

            this.Load += MainForm_Load;
        }

        private async void MainForm_Load(object sender, EventArgs e)
        {
            await BeginDownload();
        }

        /// <summary>
        /// 开始下载
        /// </summary>
        /// <returns></returns>
        private async Task BeginDownload()
        {
            //lblStatus.Text = @"正在检查更新...";
            synchronizationContext.Post(o =>
            {
                lblStatus.Text = @"正在下载更新....";
            }, null);

            // 请求接口，判断是否有最新版本
            // 如果有最新版本，则关闭主程序进程，并下载最新版本
            // 下载完成后，启动安装程序

            string savePath = await DownloadFile("HaiNanQiXingAssistant.exe");

            if (MessageBox.Show(@"下载完成，是否立即安装？", @"更新程序", MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
            {
                // 下载后启动文件
                Process process = new Process();
                process.StartInfo.FileName = savePath;
                process.Start();
            }

            Close();
        }

        /// <summary>
        /// 下载文件
        /// </summary>
        /// <param name="downloadFileName">文件的文件名</param>
        /// <returns>文件保存的完整路径</returns>
        private async Task<string> DownloadFile(string downloadFileName)
        {
            // 下载目录默认是系统临时目录
            string downloadPath = Path.GetTempPath();
            return await DownloadFile(downloadFileName, downloadPath);
        }

        /// <summary>
        /// 下载文件
        /// </summary>
        /// <param name="downloadFileName">下载的文件名</param>
        /// <param name="downloadPath">文件下载路径</param>
        /// <returns>文件保存的完整路径</returns>
        private async Task<string> DownloadFile(string downloadFileName, string downloadPath)
        {
            var client = new HttpClient();

            HttpResponseMessage response = await client.GetAsync(_address, HttpCompletionOption.ResponseHeadersRead);

            response.EnsureSuccessStatusCode();  // 检查响应成功，否则抛出异常

            _fileSize = response.Content.Headers.ContentLength.Value;

            string savePath = Path.Combine(downloadPath, downloadFileName);

            using (var fileStream = new FileStream(savePath, FileMode.Create, FileAccess.Write, FileShare.None))
            {
                await response.Content.CopyToAsync(fileStream);
            }

            return savePath;
        }
    }
}