Question

如何获取自定义类型的通用列表的第一个和最后一个元素。

嗨，我的代码中有这个通用列表

我想将已添加到列表week1中的值传递给一个函数，但是我什至无法打印出这些值，或者将其分配给另一个DateTime变量时都不能。

像Response.Write(week1[0])这样的简单东西不起作用，我什至尝试了(week1.First())，但是foreach循环却像一个符咒。我不想要，实际上我只需要一周之间的第一个和最后一个日期。

List<Week> week1 = new List<Week>();
List<Week> week2 = new List<Week>();
List<Week> week3 = new List<Week>();
List<Week> week4 = new List<Week>();
List<Week> week5 = new List<Week>();

public class Week
{
    //this class has a default constructor
    public DateTime datefortheweek { get; set; }
}

//this works fine
foreach(Week text in week1)
{
    Response.Write(text.datefortheweek);
    Response.Write("<br/>");
}

Answer 1

Response.Write(week1[0])无法正常工作可能是因为Response.Write没有将Week作为参数。

如果仔细观察，您的foreach循环方法将使用text.datefortheweek而不是text。您还应该在datefortheweek之后访问week[0]，它应该可以工作：

Response.Write(week1[0].datefortheweek);
Response.Write(week1[week1.Length - 1].datefortheweek);

我还建议您使用2D数组/列表存储Week。这样可以节省您编写week1，week2，week3 ... weekX的时间。

List<List<Week>> weeks = new List<List<Week>>();
weeks.Add(new List<Week>());
weeks.Add(new List<Week>());
weeks.Add(new List<Week>());
...

Answer 2

您需要

Response.Write(week1[0].datefortheweek)

或

Response.Write(week1.First().datefortheweek)

无法从通用列表中获取值<t>

2 个答案: