using System;

using System.Linq;

​

public class Person 

{

    public string First {get ;set;}

    public string Last {get; set;}

​

    public Person(string first, string last) 

    {

        First = first;

        Last = last;

    }

}

​

​

public class Program

{

    public static void Main()

    {

        Person p1 = new Person("larry", "page");

        Person p2 = new Person("larry", "page");

        Person p3 = new Person("serguey", "brin");      

​

        Person[] persons = new Person[3] {p1, p2, p3};

        var res = persons.GroupBy(p => p.First, p => p)

                         .Select(g => (First: g.Key, Data: g.First()))

                         .ToDictionary(tpl => tpl.First, tpl => tpl.Data, StringComparer.InvariantCultureIgnoreCase);

        //string data = @"{    ""query"": ""query MyFirstQuery { advertisable { forUser { eid name campaigns { eid name metrics(start: \""2021-06-01\"", end: \""2021-06-30\"") { summary { impressions clicks cpc cpa } } } } } }""}";

        //data.Dump();

    }

}