using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        Person bob = new Person(){Name="bob", EmailAddress="bob@abc.com"};

        Person cat = new Person(){Name="cat", EmailAddress="cat@abc.com"};

        var addressBook = new Dictionary<Person, Person>();

        addressBook.Add(bob, bob);

        addressBook.Add(cat, cat);

        var findBob = new Person(){Name = "bob"};

        var bobFound = addressBook[findBob];

        Console.WriteLine(bobFound.EmailAddress);

    }

}

​

public class Person

{

    public string Name{get;set;}

    public string EmailAddress{get;set;}

    public override bool Equals(Object obj)

    {

        return obj != null && obj is Person && ((Person)obj).Name == this.Name;

    }

    public override int GetHashCode()

    {

        return Name.GetHashCode();

    }

}