Question

I have the following code:

class Person
{
    public String Name { get; set; }
    public String LastName { get; set; }
    public String City { get; set; }

    public Person(String name, String lastName, String city)
    {
        Name = name;
        LastName = lastName;
        City = city;
    }
}

...

personList.Add(new Person("a", "b", "1"));
personList.Add(new Person("c", "d", "1"));
personList.Add(new Person("e", "f", "2"));
personList.Add(new Person("g", "h", "1"));
personList.Add(new Person("i", "j", "2"));
personList.Add(new Person("k", "l", "1"));
personList.Add(new Person("m", "n", "3"));
personList.Add(new Person("o", "p", "3"));
personList.Add(new Person("q", "r", "4"));
personList.Add(new Person("s", "t", "5"));

So then I want to group the list by Cities, and I do the following;

var result = personList.GroupBy(x => x.City);

But now what I want to do is to concatenate the items that have 1 or 3 as a City (it can be specified dynamically)

Example:

The first item on result would return an array of persons that contain cities 1, 3

Thanks!

Answer 1

You can just use a Where() filter and project each remaining group into an array using ToArray():

var result = personList.GroupBy(x => x.City)
                       .Where ( g => g.Key == someCity || g.Key == anotherCity)
                       .Select( g => g.ToArray());