Microsoft LINQ

• [Seeing the SQL Generated by LINQ to Entity Queries (Visual Studio Magazine)]
• Media:Microsoft Press - Introducing Microsoft LINQ.zip
• LINQ to XML - 5 Minute Overview
• 101 Linq samples (MSDN)
• Linq extension method to flatten a hierarchy:

using System.Collections.Generic;
using System.Linq;
using Model.Entity;
namespace Util
{
   public static class RatesWorksheetSectionExtensions
   {
       public static IEnumerable<RatesWorksheetSection> Flatten(this IEnumerable<RatesWorksheetSection> source)
       {
           return source.Concat(source.SelectMany(p => p.Children.Flatten()));
       }
   }
}