Very easy in .Net:
if (File.Exists(fileName))
{
FileInfo info = new FileInfo(fileName);
lblLastGenerated.Text = info.LastWriteTime.ToLongDateString() + " " + info.LastWriteTime.ToShortTimeString();
}
Msdn link to the fileinfo class: http://msdn.microsoft.com/en-us/library/system.io.fileinfo.aspx
