Question

我根据图书的发布时间打印所有最新记录。（PubEnd）。现在我可以按降序打印所有出版的书籍。

我需要打印20个最新发布的标题。我怎么能这样做？现在，下面的代码是打印按降序发布的所有书籍。

var query = docs.Descendants(name)
        .Select(x => new
                        {
                            Title = (string)x.Element(ns + "TITLE"),
                            Status = (string)x.Element(ns + "STATUS"),
                            PubEnd = (string)x.Element(ns + "PUB_END")

                        })                                              
        .Select(x => new
        {
            Title = x.Title,
            Status = x.Status,
            PubEnd = x.PubEnd,
        }).OrderByDescending(x => x.PubEnd).ToList();

foreach (var book in query)
{
    if (book.Status == "Published")
    {
        Response.Write(book.Title);
        Response.Write(book.Status);
        Response.Write(book.PubEnd);
    }
}

Answer 1

使用Take()：

foreach (var book in query.Take(20))
{
   //print
}

如果总是，则只需要相应地更新查询本身：

(..).OrderByDescending(x => x.PubEnd).Take(20).ToList();

Answer 2

您应该只需要使用Take(20)

Here is the documentation on Take

您的代码将变为：

...OrderByDescending(x => x.PubEnd).Take(20).ToList()

DISTINCT更新

Here is the documentation for Distinct

你的代码就是这样，我假设你在20岁之前想要分开：）

...OrderByDescending(x => x.PubEnd).Distinct().Take(20).ToList()

Answer 3

使用Take(20)
为什么要使用相同的值构建两次无差别的对象？

这应该是你需要的：

var list = docs.Descendants(name)
               .Select(x => new
                    {
                        Title = (string)x.Element(ns + "TITLE"),
                        Status = (string)x.Element(ns + "STATUS"),
                        PubEnd = (string)x.Element(ns + "PUB_END")
                    })
               .OrderByDescending(x => x.PubEnd).Take(20).ToList();

如果您想获得截然不同的结果：

var list = (...).OrderByDescending(x => x.PubEnd).Distinct().Take(20).ToList();

Answer 4

var query = docs.Descendants(name)
.Select(x => new
{
    Title = (string)x.Element(ns + "TITLE"),
    Status = (string)x.Element(ns + "STATUS"),
    PubEnd = (string)x.Element(ns + "PUB_END")

})
.OrderByDescending(x => x.PubEnd).Take(20); // Take will get the first N records.

foreach (var book in query)
{
    if (book.Status == "Published")
    {
        Response.Write(book.Title);
        Response.Write(book.Status);
        Response.Write(book.PubEnd);
    }
}

按日期排序打印仅在LINQ中的最新20条记录

4 个答案: