完成下载后，如何在listview项目中添加另一个子项目？

Question

我有一个listview控件和一个按钮的应用程序。 当我按下按钮时，我希望它将文件的时间和名称添加到列表视图中，然后将其添加到控件中，一旦完成下载文件，我希望它将另一个子项添加到同一列表视图中，但由于某种原因它没有添加它我无法弄清楚为什么，我说错了什么？

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

namespace Listviews
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        ListViewItem lvi = new ListViewItem();
        WebClient webClient;


        public void DownloadFile(string urlAddress, string location)
        {
            using (webClient = new WebClient())
            {
                webClient.DownloadFileCompleted += new AsyncCompletedEventHandler(Completed);

                try
                {
                    // Start downloading the file
                    webClient.DownloadFileAsync(new System.Uri(urlAddress), location);
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message);
                }
            }
        }

        // The event that will trigger when the WebClient is completed
        private void Completed(object sender, AsyncCompletedEventArgs e)
        {
            if (e.Cancelled == true)
            {
                MessageBox.Show("Download has been canceled.");
            }
            else
            {
                ListViewItem lvItems = new ListViewItem();
                lvItems.SubItems.Add("Done");
                listView1.Items.Add(lvItems);
            }
        }


        private void btnAdd_Click(object sender, EventArgs e)
        {
            ListViewItem lvItems = new ListViewItem();
            string clock = DateTime.Now.ToString("HH:mm");
            lvItems.Text = clock;
            listView1.Items.Add(lvItems);

            string requestUrl = "url";
            string fileName = "\\Name";
            string savePath = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);

            string combinedPaths = savePath + fileName;
            DownloadFile(requestUrl, combinedPaths);
        }
    }
}