像IDM一样自动捕获下载链接

这是我下载文件的代码 我正在传递一个URL，但我想让我的下载管理器自动捕获链接

   private void button1_Click_1(object sender, EventArgs e)
    {
        WebClient client = new WebClient();
    client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(ProgressChanged);
    client.DownloadFileCompleted += new AsyncCompletedEventHandler(client_DownloadFileCompleted);
    string []filename;
        string fn ; fn=textBox1.Text;
        int i;
    filename =fn.Split('/');
    for (i = 1; i <= filename.Length; i++) ;
        string oname=filename[i-2];
    //////// Starts the download
    client.DownloadFileAsync(new Uri("http://dinirah.wen.ru/Internet-k-zariye-musalmano-gumrah-kia-ja-raha.mp3"), textBox2.Text+"''"+oname);
      //////// the above i passed the url to download.
        label4.Text = i.ToString();
    button1.Text = "Download In Process";
    button1.Enabled = false;
    }

现在我想让我的下载器自动获取下载网址，并将其存储在一个字符串中，然后作为URL传递。