using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var productInformationItems = new List<ProductTermAndPricingDataItem>();

        productInformationItems.Add(new ProductTermAndPricingDataItem(125,"Month",(decimal)10.00,"Wholesale"));

        productInformationItems.Add(new ProductTermAndPricingDataItem(125,"Year",(decimal)20.00,"Wholesale"));

        productInformationItems.Add(new ProductTermAndPricingDataItem(126,"Month",(decimal)20.00,"Wholesale"));

        productInformationItems.Add(new ProductTermAndPricingDataItem(126,"Year",(decimal)30.00,"Wholesale"));

        productInformationItems.Add(new ProductTermAndPricingDataItem(127,"Month",(decimal)40.00,"Wholesale"));

        productInformationItems.Add(new ProductTermAndPricingDataItem(127,"Year",(decimal)50.00,"Wholesale"));

        List<ProductPricingGetDataItem> grouped = productInformationItems.GroupBy(

                                        p => p.ProductID,

                                        (key, g) => new ProductPricingGetDataItem() { ProductID = key, Terms = g.Select(x => new Terms(x.BillingPeriodName, x.PriceAmount)).ToList() }).ToList();

        foreach(ProductPricingGetDataItem item in grouped)

        {

            Console.WriteLine(item);

        }

    }

}

​

public class ProductTermAndPricingDataItem {

    public int ProductID { get; set; }

    public string BillingPeriodName { get; set; }

    public decimal PriceAmount { get; set; }

    public string PriceTypeName { get; set; }

    // for demo purposes

    public ProductTermAndPricingDataItem(int id, string period, decimal amount, string priceType) {

        ProductID = id;

        BillingPeriodName = period;

        PriceAmount = amount;

        PriceTypeName = priceType;

    }

}

​

public class ProductPricingGetDataItem

{

​

    public int ProductID { get; set; }    

    private List<Terms> _terms = new List<Terms>();

    public List<Terms> Terms

    {

        get { return _terms; }

        set { _terms = value; }

    }

    public override string ToString()

    {

        return string.Format("{0} => [{1}]", ProductID, String.Join(" | ", Terms.Select(x => x.ToString())));

    }

}

​

public class Terms

{

    public string Term { get; set; }

    public decimal Price { get; set; }

    // Necessary

    public Terms(string term, decimal price)

    {

        Term = term;

        Price = price;

    }

    public override string ToString()

    {

        return string.Format("{0};{1}", Term, Price);

    }

}