var query = from l in list

group l by new {A=l.A,B=l.B} into g

select g;

var query2 = from g in query

group g by g.Key.A into x

select x;

//然后query和query2合并结果

/// <summary>

/// Adds sub-totals to a list of items, along with a grand total for the whole list.

/// </summary>

/// <param name="elements">Group and/or sort this yourself before calling WithRollup.</param>

/// <param name="primaryKeyOfElement">Given a TElement, return the property that you want sub-totals for.</param>

/// <param name="calculateSubTotalElement">Given a group of elements, return a TElement that represents the sub-total.</param>

/// <param name="grandTotalElement">A TElement that represents the grand total.</param>

public static List<TElement> WithRollup<TElement, TKey>(this IEnumerable<TElement> elements,

    Func<TElement, TKey> primaryKeyOfElement,

    Func<IGrouping<TKey, TElement>, TElement> calculateSubTotalElement,

    TElement grandTotalElement)

{

    // Create a new list the items, subtotals, and the grand total.

    List<TElement> results = new List<TElement>();

    var lookup = elements.ToLookup(primaryKeyOfElement);

    foreach (var group in lookup)

    {

        // Add items in the current group

        results.AddRange(group);

        // Add subTotal for current group

        results.Add(calculateSubTotalElement(group));

    }

    // Add grand total

    results.Add(grandTotalElement);



    return results;

}

class Program

{

    static void Main(string[] args)

    {

        IQueryable<CustomObject> dataItems = (new[]

        {

            new CustomObject { City = "Seattle", Plan = "Plan B", Charges = 20 },

            new CustomObject { City = "Seattle", Plan = "Plan A", Charges = 10 },

            new CustomObject { City = "Seattle", Plan = "Plan B", Charges = 20 },

            new CustomObject { City = "Seattle", Plan = "Plan A", Charges = 10 },

            new CustomObject { City = "Seattle", Plan = "Plan A", Charges = 10 },

            new CustomObject { City = "Seattle", Plan = "Plan A", Charges = 10 },

            new CustomObject { City = "Portland", Plan = "Plan A", Charges = 10 },

            new CustomObject { City = "Portland", Plan = "Plan A", Charges = 10 },

            new CustomObject { City = "Portland", Plan = "Plan C", Charges = 30 },

            new CustomObject { City = "Portland", Plan = "Plan C", Charges = 30 },

            new CustomObject { City = "Portland", Plan = "Plan C", Charges = 30 }

        }).AsQueryable();



        IQueryable<CustomObject> orderedElements = from item in dataItems

                                                   orderby item.City, item.Plan

                                                   group item by new { item.City, item.Plan } into grouping

                                                   select new CustomObject

                                                   {

                                                       City = grouping.Key.City,

                                                       Plan = grouping.Key.Plan,

                                                       Charges = grouping.Sum(item => item.Charges),

                                                       Count = grouping.Count()

                                                   };



        List<CustomObject> results = orderedElements.WithRollup(

            item => item.City,

            group => new CustomObject

            {

                City = group.Key,

                Plan = "All",

                Charges = group.Sum(item => item.Charges),

                Count = group.Sum(item => item.Count)

            },

            new CustomObject

            {

                City = "All",

                Plan = "All",

                Charges = orderedElements.Sum(item => item.Charges),

                Count = orderedElements.Sum(item => item.Count)

            });



        foreach (var result in results)

            Console.WriteLine(result);



        Console.Read();

    }

}



class CustomObject

{

    public string City { get; set; }

    public string Plan { get; set; }

    public int Count { get; set; }

    public decimal Charges { get; set; }



    public override string ToString()

    {

        return String.Format("{0} - {1} ({2} - {3})", City, Plan, Count, Charges);

    }

}