如何將新項目添加到對象列表的特定 position

Question

我有兩個對象列表（authors1，authors2），注意 authors1 已經按 SDATE 排序，我想做的是將 authors2 項目添加到 authors1 中，保持相同的順序，注意添加的所有新項目都需要 go 到末尾每組物品

IList<Author> authors1 = new List<Author>
{
    new Author { Book = "c#", Code="A11" , SDate = 1 },
    new Author { Book = "c#", Code="A22" , SDate = 1 },
    new Author { Book = "c#", Code="A31" , SDate = 1 },

    new Author { Book = "js", Code="B43" , SDate = 2 },
    new Author { Book = "js", Code="B33" , SDate = 2 },
    new Author { Book = "js", Code="B41" , SDate = 2 },

    new Author { Book = "java", Code="C27", SDate = 3 },
    new Author { Book = "java", Code="C33", SDate = 3 },
    new Author { Book = "java", Code="C78", SDate = 3 }
};

IList<Author> authors2 = new List<Author>
{
    new Author { Book = "c#", Code = "A21" },
    new Author { Book = "java", Code = "C23" }
};

預期的

IList<Author> authors1 = new List<Author>
{
    new Author { Book = "c#", Code="A11", SDate = 1 },
    new Author { Book = "c#", Code="A22", SDate = 1 },
    new Author { Book = "c#", Code="A31", SDate = 1 },
    new Author { Book = "c#", Code="A21", SDATE = 1 },  // new item added to the end of this group

    new Author { Book = "js", Code="B43", SDate = 2 },
    new Author { Book = "js", Code="B33", SDate = 2 },
    new Author { Book = "js", Code="B41", SDate = 2 },

    new Author { Book="java", Code="C27", SDate=3 },
    new Author { Book="java", Code="C33", SDate=3 },
    new Author { Book="java", Code="C78", SDate=3 },
    new Author { Book="java", Code="C23", SDATE=3 }  // new item added to the end of this group
};

我怎樣才能完成這個功能？

我正在嘗試使用兩個 foreach，然后將這些項目推送到一個新列表中，請幫忙

    IList<Author> response = new List<Author>();

    foreach (var author in authors2.GroupBy(x => x.Book).ToList())
    {
        foreach (var item in author)
        {

Answer 1

你可以這樣做：

foreach(Author a in authors2)
{
    Author b = authors1.Where(x => x.Book == a.Book).LastOrDefault();
    if (b != null)
    {
        int index = authors1.IndexOf(b);
        a.SDate = b.SDate;
        authors1.Insert(index + 1, a);
    }
}