private void button2_Click(object sender, EventArgs e)
{
for (int i=0; i<=listBox1.Items.Count; i++)
{
var desktop = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
string fileName = desktop + "\\" + i +".mp3";
WebClient webClient = new WebClient();
webClient.DownloadFile(listBox1.Items[i].ToString(), fileName);
}
}