Question

I have the following list:

    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"));

How do I retrieve a list of persons differing from the city name?

Expecting Results:

An Array/Collection of lists (persons) differing from the city name:

result[0] = List<Person> where city name = "1"
result[1] = List<Person> where city name = "2"
result[n] = List<Person> where city name = "whatever"

Answer 1

You could use LINQ to group the persons list by city:

var groupedPersons = personList.GroupBy(x => x.City);
foreach (var g in groupedPersons)
{
    string city = g.Key;
    Console.WriteLine(city);
    foreach (var person in g)
    {
        Console.WriteLine("{0} {1}", person.Name, person.LastName);
    }
}