我试图利用’包含’来模拟旧的sql’,其中id为(1,2,3,4)’过滤查询的方式.
但是我在使用它时遇到了一些困难,因为我的身份处于更深层次.
码：
public class Category
{
public long Id { get; set; }
public string Name { get; set; }
}
public class Characteristica
{
public Category Category { get; set; }
public int Id { get; set; }
public string Value { get; set; }
}
public class Person
{
public string Name { get; set; }
public List<Characteristica> Appearance { get; set; }
}
class Program
{
static void Main(string[] args)
{
var persons = new List<Person>
{
new Person { Name = "Person A",Appearance = new List<Characteristica> { new Characteristica { Id = 22 },new Characteristica { Id = 5 },new Characteristica { Id = 12 } }},new Person { Name = "Person B",Appearance = new List<Characteristica> { new Characteristica { Id = 1 },new Characteristica { Id = 6 },new Characteristica { Id = 11 } }},new Person { Name = "Person C",Appearance = new List<Characteristica> { new Characteristica { Id = 2 },new Characteristica { Id = 8 },new Characteristica { Id = 13 } }},new Person { Name = "Person D",new Characteristica { Id = 10 } }},new Person { Name = "Person E",new Person { Name = "Person F",new Characteristica { Id = 23 } }},};
var listOfSearchedIds = new List<int> { 22,23 };
var selected = persons.Select(p => p.Appearance.Where(a => listOfSearchedIds.Contains(a.Id))).ToList();
}
}
现在我试图通过使用contains feauture从我的收藏中获取’Person A’和’Person F’.但是我无法看到我在这里做错了什么.
解决方法
你的方式是正确的,但你应该使用Where而不是Select
var selected = persons.Where(p => p.Appearance
.Where(a => listOfSearchedIds.Contains(a.Id))
.Any()).ToList();
并且您需要使用Any来检查p.Appearance.Where中的返回序列是否包含任何元素.或者您可以直接使用Any并使其更短：
var selected = persons.Where(p => p.Appearance
.Any(a => listOfSearchedIds.Contains(a.Id))
.ToList();
