winform 下载程序

您可以使用 C# 编写一个 WinForm 下载程序，以下是一个简单的示例：

using System;
using System.ComponentModel;
using System.Windows.Forms;
using System.Net;

namespace DownloadManager
{
    public partial class MainForm : Form
    {
        private WebClient webClient;

        public MainForm()
        {
            InitializeComponent();
        }

        private void btnDownload_Click(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(txtUrl.Text))
            {
                MessageBox.Show("请先输入下载链接！");
                return;
            }

            if (webClient != null)
            {
                MessageBox.Show("当前已有下载任务！");
                return;
            }

            webClient = new WebClient();
            webClient.DownloadProgressChanged += WebClient_DownloadProgressChanged;
            webClient.DownloadFileCompleted += WebClient_DownloadFileCompleted;

            string fileName = txtUrl.Text.Substring(txtUrl.Text.LastIndexOf("/") + 1);
            string savePath = AppDomain.CurrentDomain.BaseDirectory + fileName;

            webClient.DownloadFileAsync(new Uri(txtUrl.Text), savePath);
        }

        private void WebClient_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
        {
            progressBar.Value = e.ProgressPercentage;
            lblProgress.Text = $"{e.ProgressPercentage}% ({e.BytesReceived / 1024}KB/{e.TotalBytesToReceive / 1024}KB)";
        }

        private void WebClient_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
        {
            webClient.Dispose();
            webClient = null;

            if (e.Error != null)
            {
                MessageBox.Show($"下载出错：{e.Error.Message}");
                return;
            }

            MessageBox.Show("下载完成！");
        }
    }
}