C# linq expression in lambda with contains

Question

I am trying to make use of the 'contains' to simulate the old SQL 'where id in (1,2,3,4)' way of filtering a query. However I have some difficulties in using it where my id's are in a deeper level. Code: ``` 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 Appearance { get; set; } } class Program { static void Main(string[] args) { var persons = new List { new Person { Name = "Person A", Appearance = new List { new Characteristica { Id = 22 }, new Characteristica { Id = 5 }, new Characteristica { Id = 12 } }}, new Person { Name = "Person B", Appearance = new List { new Characteristica { Id = 1 }, new Characteristica { Id = 6 }, new Characteristica { Id = 11 } }}, new Person { Name = "Person…

Accepted Answer

Your way is correct but you should use `Where` instead of `Select`

```
 var selected = persons.Where(p => p.Appearance
                .Where(a => listOfSearchedIds.Contains(a.Id))
                .Any()).ToList();
```

And you need to use `Any` to check whether the returning sequence from `p.Appearance.Where` contains any element.Or you can use `Any` directly and make it shorter:

```
var selected = persons.Where(p => p.Appearance
                .Any(a => listOfSearchedIds.Contains(a.Id))
                .ToList();
```

C# linq expression in lambda with contains

Solution

Problem