public partial class frmMain : Form
    {
        public frmMain()
        {
            InitializeComponent();
        }

        private void btnStart_Click(object sender, EventArgs e)
        {
            WebClient webClient = new WebClient();
            webClient.Headers.Add("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)");

            int iPos = txtAddress.Text.LastIndexOf('/');
            webClient.DownloadFile(txtAddress.Text, txtAddress.Text.Substring(iPos + 1));
        }
    }