using System;
using System.Linq;

public class Test
{
	public static void Main()
	{
var products = new [] {
	new { Name="A", Priority="1", Value=default(string) },
	new { Name="A", Priority="2", Value=default(string) },
	new { Name="A", Priority="3", Value="10" },
	new { Name="A", Priority="4", Value=default(string) },
	new { Name="A", Priority="5", Value="20" },
	new { Name="A", Priority="6", Value=default(string) },
	new { Name="B", Priority="1", Value="15" },
	new { Name="B", Priority="2", Value=default(string) },
	new { Name="B", Priority="3", Value="10" },
	new { Name="B", Priority="4", Value=default(string) },
	new { Name="B", Priority="5", Value="20" },
	new { Name="B", Priority="6", Value=default(string) },
};

var result = products
	.GroupBy(p => p.Name)
	.SelectMany (grp =>
		grp.OrderBy(p => p.Priority)            // sort by priority
			.SkipWhile(p => p.Value == null)     // skip null entries at beginnig
			.Reverse()                           // reverse
			.SkipWhile(p => p.Value == null)     // skip null entries at end
			.Reverse()                           // reverse back to normal
			.Where(p => p.Value == null)        // then find null entries
	);

foreach (var product in result)
{
	Console.WriteLine("Product(Name=" + product.Name + ",Priority=" + product.Priority + ",Value=" + product.Value + ")");
}
	}
}