LINQ查询选择前五名

Question

我有一个LINQ查询:

var list = from t in ctn.Items
           where t.DeliverySelection == true && t.Delivery.SentForDelivery == null
           orderby t.Delivery.SubmissionDate
           select t;

如何修改此查询以从数据库中仅选择五个结果？

Answer 1

var list = (from t in ctn.Items
           where t.DeliverySelection == true && t.Delivery.SentForDelivery == null
           orderby t.Delivery.SubmissionDate
           select t).Take(5);

Answer 2

解决方案:

var list = (from t in ctn.Items
           where t.DeliverySelection == true && t.Delivery.SentForDelivery == null
           orderby t.Delivery.SubmissionDate
           select t).Take(5);

Answer 3

这也可以使用Linq的基于Lambda的方法来实现;

var list = ctn.Items
.Where(t=> t.DeliverySelection == true && t.Delivery.SentForDelivery == null)
.OrderBy(t => t.Delivery.SubmissionDate)
.Take(5);

Answer 4

[提供比@Ajni提供的答案更具描述性的答案.]

这也可以使用LINQ 流畅的语法实现:

var list = ctn.Items
    .Where(t=> t.DeliverySelection == true && t.Delivery.SentForDelivery == null)
    .OrderBy(t => t.Delivery.SubmissionDate)
    .Take(5);

注意,每一种方法(Where,OrderBy,Take出现在此LINQ语句)需要一个lambda表达式作为参数.另请注意,文档Enumerable.Take以:

从序列的开头返回指定数量的连续元素.

Answer 5

Additional information

有时有必要将模型绑定到视图模型中并给出类型转换错误。在这种情况下，您应该使用ToList()方法。

var list = (from t in ctn.Items
       where t.DeliverySelection == true && t.Delivery.SentForDelivery == null
       orderby t.Delivery.SubmissionDate
       select t).Take(5).ToList();