using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public void Main()

    {             

        var searchResults = CreateSource();

​

        var finalResults =

            from srGroup in searchResults.GroupBy(sr => sr.article)

            let prices = srGroup.SelectMany(sr => sr.prices).ToDictionary(p => p.Key, p => p.Value)

            let article = srGroup.First().article

            select new PricedDrug { article = article, prices = prices };

        foreach (var res in finalResults)

        {

            foreach (var price in res.prices)

                Console.Write(price.Key + " " + price.Value + " ");

            Console.WriteLine("~ " + res.article);

        }

    }   

    public static IEnumerable<PricedDrug> CreateSource()

    {

        return new List<PricedDrug> {

            new PricedDrug { prices = new Dictionary<string, float> { { "site1", 100 } }, article = "1" },

            new PricedDrug { prices = new Dictionary<string, float> { { "site2", 110 } }, article = "1" },

            new PricedDrug { prices = new Dictionary<string, float> { { "site3", 10 } }, article = "2" },

            new PricedDrug { prices = new Dictionary<string, float> { { "site2", 12 } }, article = "2" },

        };

    }   

}

​

public class PricedDrug: IComparable<PricedDrug>

    {

        public PricedDrug()

        {

            prices = new Dictionary<string, float>();

        }

        public string article;

        public Dictionary<string, float> prices;

        public int CompareTo(PricedDrug other)

        {

            return article.CompareTo(other.article);

        }

    }

​