Question

I want know to make a query using linq, between a collection of objects
and a collection of values. In the sample code below, I make the question about it.

class USER
{
    public string Name { get; set; }
}

public class MyClass
{
    public MyClass()
    {
        List<USER> listUser = new List<USER>();
        listUser.Add(new USER { Name = "A" });
        listUser.Add(new USER { Name = "B" });
        listUser.Add(new USER { Name = "C" });
        listUser.Add(new USER { Name = "D" });

        string[] arrayNames = { "A", "B" };
    }
}

Using Linq how can I get all USER in listUser with them Name equals to the arrayNames values.?

The expected results wold be

        //listUser[0] --> User with Name == "A"
        //listUser[1] --> User with Name == "B"

Thanks in advance.

Answer 1

HashSet<string> names = new HashSet<string>(new string[]{ "A", "B" });
var selectedUsers = listUser.Where(user => names.Contains(user.Name));

The hashset is optional and overkill if you have only a few users but it guarantees optimal lookup performance if you have a lot of users.