重载的ToString不会出现在intellisense中

Question

我在youtube处接受了教程。在8:04，讲师附加了本地方法来重载ToString，当我尝试做同样的事情时，我没有看到intellisense中的重载方法。

 public class Person
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public DateTime StartDate { get; set; }
        public int Rating { get; set; }

        public override string ToString()
        {
            return string.Format("{0} {1}", FirstName, LastName);
        }

        public string ToString(PersonFormat format)
        {
           return format(this);
        }

我尝试添加关键字覆盖它也不起作用。看起来像我在某处遗漏了某些东西。

Answer 1

这是因为var隐藏了person的实际类型，该PersonListBox.Items是通过foreach(Person person in PersonListBox.Items) { } 访问时的对象。以下作品：

foreach(var person in PersonListBox.Items)
{
    // person is object. It doesn't have the method you want to call. 
    // it even doesn't have FirstName or LastName
    // try person. and you can clearly see it only has the common
    // object methods.
}

while：

foreach(var p in PersonListBox.Items.OfType<Person>())

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