int.TryParse(year, out y)

 int y;
 if (!int.TryParse(year, out y))
  {
       y = DateTime.Now.Year;
 }
 this.lbYearNow.Text = y.ToString();

当year为null时此时int.TryParse(year, out y)为false;会执行y=DateTime.Now.Year;y.ToString()=当前年；

当year为2011，2012时，此时int.TryParse(year,out y)为true;此时y=2011,2012,不会执行y=DateTime.Now.Year;