c# - 在集合中添加增量索引号

Question

public class Comment
{
    public int IndexNo {get;set;}
    public DateTime CreatedOn {get;set;}
}

static void Main()
{
    int i = 0;
    var comments = new List<Comment>()
    {
        new Comment() { CreatedOn = DateTime.Now.AddMinutes(1) },
        new Comment() { CreatedOn = DateTime.Now.AddMinutes(2) },
        new Comment() { CreatedOn = DateTime.Now.AddMinutes(3) },
        new Comment() { CreatedOn = DateTime.Now.AddMinutes(4) },
    };

    // Not very nice solution..
    var foos = new List<Comment>();
    foreach(var foo in comments.orderby(c=> c.createdOn))
    {
        foo.IndexNo = ++i;
        foos.add(foo);
    }

}

如何从列表中为 IndexNo 属性分配一些增量编号？我的预期输出是:

• 2004 年 4 月 15 日下午 2:37 ~ 1
• 2004 年 4 月 15 日下午 2:38 ~ 2
• 2004 年 4 月 15 日下午 2:39 ~ 3
• 2004 年 4 月 15 日下午 2:40 ~ 4

谢谢。

Answer 1

回复评论:

Actually I was hoping to assign the increment IndexNo, after the collection has been created.

然后循环:

int i = 1;
foreach(var comment in comments) comment.IndexNo = i++;

---

由于您正在对偏移量进行硬编码，因此您可以硬编码:

var comments = new List<Comment>() {
    new Comment() { CreatedOn = DateTime.Now.AddMinutes(1), IndexNo = 1 },
    new Comment() { CreatedOn = DateTime.Now.AddMinutes(2), IndexNo = 2 },
    new Comment() { CreatedOn = DateTime.Now.AddMinutes(3), IndexNo = 3 },
    new Comment() { CreatedOn = DateTime.Now.AddMinutes(4), IndexNo = 4 },
};

如果你想要一些不那么硬编码的东西，怎么样:

var comments = (from i in Enumerable.Range(1,4)
                select new Comment {
                   CreatedOn = DateTime.Now.AddMinutes(i), IndexNo = i
                }).ToList();

或更简单:

var comments = new List<Comment>(4);
for(int i = 1 ; i < 5 ; i++) {
    comments.Add(new Comment {
         CreatedOn = DateTime.Now.AddMinutes(i), IndexNo = i });
}