using System;

using System.Collections.Generic;

​

using System.Linq;

public class Program

{

    public static void Main()

    {

        var groups = Person.MergePerson(Person.r);

            foreach (var group in groups)

            {

                Console.WriteLine("Группа: " + group.Key);

                foreach (Person person in group.Value)

                {

                    Console.WriteLine(@"Person {0} {1} {2}", person.a, person.b, person.ndx);

                }

            }

    }

    public  class Person

        {

            public string a;

            public string b;

            public int ndx;

​

            public  Person(string a, string b, int ndx)

            {

                this.a = a;

                this.b = b;

                this.ndx = ndx;

​

            }

​

            public static List<Person> r = new List<Person> {

​

                 new Person("10", "1", 0),

​

                 new Person("10", "0", 1),

​

                 new Person("10", "2", 2),

​

                 new Person("13", "4", 3),

​

                 new Person("11", "2", 4),

​

                 new Person("11", "3", 5),

​

                 new Person("12", "3", 6),

​

                 new Person("14", "5", 7),

​

                 new Person("13", "5", 8),

​

                 };

​

            public static Dictionary<string, List<Person>> MergePerson(List<Person> r)

            {

                return new Dictionary<string, List<Person>>

                {

                    {"a", r.GroupBy(x => x.a).Where(y => y.Count() > 1).SelectMany(z => z).ToList()},

                    {"b", r.GroupBy(x => x.b).Where(y => y.Count() > 1).SelectMany(z => z).ToList()}

                };

​

​

            }

​

​

        }

}