Thread thread.IsBackground =true;
//Gets or sets a value indicating whether or not a thread is a background thread.
//获取或设置一个值，该值指示某个线程是否为后台线程。
命名空间： System.Threading
true if this thread is or is to become a background thread; otherwise,false.
如果此线程是后台线程或即将成为后台线程，则为true；否则为false。