using System;
using System.Collections.Generic;
using System.Linq;

class Product
{
    public string Name { get; set; }
    public string Price { get; set; }
}

public class Test
{
    public static void Main()
    {
        List<Product> sourceProductList = new List<Product>
        {
            new Product { Name = "Cornflakes", Price = "1.99M"},
            new Product { Name = "Cornflakes", Price = "1.89M"},
            new Product { Name = "Rice Krispies", Price = "2.09M"},
            new Product { Name = "Cornflakes", Price = "2.09M"},
        };

        var result = sourceProductList
            .GroupBy(x => x.Name)
            .Where(g => g.Select(x => x.Price).Distinct().Count() == 1)
            .Select(g => g.First());

        foreach (Product product in result)
        {
            Console.WriteLine("Name: {0}, Price: {1}", product.Name, product.Price);
        }
    }
}