foreach新解

Posted 2020-11-24 yexiaoyanzi

 

Person[] peopleArray = new Person[3]
{
      new Person("张三", 15),
      new Person("李四", 18),
      new Person("王五", 21),
};
People peopleList = new People(peopleArray);


//第一种方法(foreach)
foreach (Person p in peopleList)
{
     Console.WriteLine(p.Name + "	" + p.Age);
}

//第二种方法(while)
IEnumerator enumeratorSimple = peopleList.GetEnumerator();
while (enumeratorSimple.MoveNext())
{
     Person p = enumeratorSimple.Current as Person;
     Console.WriteLine(p?.Name + "	" + p?.Age);
}

 

 

当我们试图给item变量赋值的时候，vs智能提示，因为是迭代变量，无法赋值，也就是说当前变量是只读的，不能赋值，那基于这种情况，我们怎么整呢？

其实，foreach已经为我们提供了解决此问题的方法：用ref 迭代变量来设置 stackalloc 数组中每个项的值，具体代码如下：

 

List<int> countList = new List<int>() {0, 1, 2, 3, 4, 5};
foreach (ref var item in countList)
{
     item++;
}