c# .net 4.0下载https文件

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;

namespace WindowsFormsApp8
{
    using System;
    using System.IO;
    using System.Net;
    using System.Windows.Forms;

    public class HttpsDownloaderNet40
    {
        public bool DownloadFileWithProgress(string url, string savePath, ProgressBar progressBar, Label statusLabel)
        {
            try
            {
                // 配置 HTTPS 安全协议（.NET 4.0 支持 TLS 1.0/SSL 3.0）
                ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Ssl3;
                ServicePointManager.SecurityProtocol |= (SecurityProtocolType)0x0300 | (SecurityProtocolType)0x0C00;
                // 忽略 SSL 证书验证（仅测试环境，生产环境需移除）
                ServicePointManager.ServerCertificateValidationCallback +=
                    (sender, cert, chain, errors) => true;

                using (WebClient client = new WebClient())
                {
                    // 绑定进度更新事件（UI 线程安全）
                    client.DownloadProgressChanged += (sender, e) =>
                    {
                        if (progressBar != null && progressBar.InvokeRequired)
                        {
                            progressBar.Invoke((MethodInvoker)(() => UpdateProgress(progressBar, e.ProgressPercentage)));
                        }
                        else
                        {
                            UpdateProgress(progressBar, e.ProgressPercentage);
                        }

                        if (statusLabel != null && statusLabel.InvokeRequired)
                        {
                            statusLabel.Invoke((MethodInvoker)(() => UpdateStatus(statusLabel, e)));
                        }
                        else
                        {
                            UpdateStatus(statusLabel, e);
                        }
                    };

                    // 绑定下载完成事件
                    client.DownloadFileCompleted += (sender, e) =>
                    {
                        if (e.Error != null)
                        {
                            ShowMessageBox("下载失败：" + e.Error.Message, MessageBoxIcon.Error);
                        }
                        else
                        {
                            ShowMessageBox("文件下载完成！", MessageBoxIcon.Information);
                        }
                    };

                    // 开始异步下载（避免 UI 阻塞）
                    client.DownloadFileAsync(new Uri(url), savePath);
                }
            }
            catch (Exception ex)
            {
                return false;
            }
            return true;
        }

        // 辅助方法：更新进度条
        private void UpdateProgress(ProgressBar progressBar, int percentage)
        {
            if (progressBar != null)
            {
                progressBar.Value = percentage;
                progressBar.Update(); // 强制刷新（可选）
            }
        }

        // 辅助方法：更新状态标签
        private void UpdateStatus(Label statusLabel, DownloadProgressChangedEventArgs e)
        {
            if (statusLabel != null)
            {
                statusLabel.Text = $"下载进度：{e.ProgressPercentage}%  " +
                                 $"{e.BytesReceived}/{e.TotalBytesToReceive} 字节";
                statusLabel.Update(); // 强制刷新（可选）
            }
        }

        // 辅助方法：跨线程显示消息框
        private void ShowMessageBox(string message, MessageBoxIcon icon)
        {
            if (MessageBox.Show(message, "提示", MessageBoxButtons.OK, icon) == DialogResult.OK)
            {
                // 可选：下载失败后清理不完整文件
                // if (icon == MessageBoxIcon.Error && File.Exists(savePath)) File.Delete(savePath);
            }
        }
    }
     
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;

namespace WindowsFormsApp8
{
    using System;
    using System.IO;
    using System.Net;
    using System.Windows.Forms;

    public class HttpsDownloaderNet40
    {
        public bool DownloadFileWithProgress(string url, string savePath, ProgressBar progressBar, Label statusLabel)
        {
            try
            { 
                ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls | SecurityProtocolType.Ssl3;
                ServicePointManager.SecurityProtocol |= (SecurityProtocolType)0x0300 | (SecurityProtocolType)0x0C00; 
                ServicePointManager.ServerCertificateValidationCallback +=
                    (sender, cert, chain, errors) => true;

                using (WebClient client = new WebClient())
                {
                    
                    client.DownloadFile(new Uri(url), savePath);
                }
            }
            catch (Exception ex)
            {
                return false;
            }
            return true;
        }
         
    } 
}