选中和取消选中作为范围

关键字还可以创建范围以便（取消）检查多个操作。

short m = 32767;
short n = 32767;
checked
{
    int result1 = (short)(m + n); //will throw an OverflowException
}
unchecked
{
    int result2 = (short)(m + n); // will return -2
}