upload file file

If FileUpload1.PostedFile.ContentLength > 0  Then
    Dim file As String = Server.MapPath("UploadedFiles/" & PostedFile.FileName);
    FileUpload1.SaveAs(file);
End If

Public Shared Sub DownloadFile(FileName As String)
    If File.Exists(FileName) Then
        Dim strFileName As String = Path.GetFileName(FileName).Replace(" ", "%20")
        HttpContext.Current.Response.ContentType = "application/octet-stream"
        HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" & strFileName)
        HttpContext.Current.Response.Clear()
        HttpContext.Current.Response.WriteFile(FileName)
        HttpContext.Current.Response.[End]()
    End If
End Sub