ObjectQuery<T>.GroupBy Method

    using (AdventureWorksEntities context =
        new AdventureWorksEntities())
    {
        string queryString = @"SELECT VALUE product 
            FROM AdventureWorksEntities.Products AS product";

        ObjectQuery<Product> productQuery =
            new ObjectQuery<Product>(queryString,
                context, MergeOption.NoTracking);

        ObjectQuery<DbDataRecord> productQuery2 =
            productQuery.GroupBy("it.name AS pn",
            "Sqlserver.COUNT(it.Name) as count, pn");

        // Iterate through the collection of Products
        // after the GroupBy method was called.
        foreach (DbDataRecord result in productQuery2)
        {
            Console.WriteLine("Name: {0}; Count: {1}",
                result["pn"], result["count"]);
        }
    }
}

using (AdventureWorksEntities context =
    new AdventureWorksEntities())
{
    // Define the query with a GROUP BY clause that returns
    // a set of nested LastName records grouped by first letter.
    ObjectQuery<DbDataRecord> query =
        context.Contacts
        .GroupBy("SUBSTRING(it.LastName, 1, 1) AS ln", "ln")
        .Select("it.ln AS ln, (SELECT c1.LastName " +
        "FROM AdventureWorksEntities.Contacts AS c1 " +
        "WHERE SubString(c1.LastName, 1, 1) = it.ln) AS CONTACT")
        .OrderBy("it.ln");

    // Execute the query and walk through the nested records.
    foreach (DbDataRecord rec in
        query.Execute(MergeOption.AppendOnly))
    {
        Console.WriteLine("Last names that start with the letter '{0}':",
                    rec[0]);
        List<DbDataRecord> list = rec[1] as List<DbDataRecord>;
        foreach (DbDataRecord r in list)
        {
            for (int i = 0; i < r.FieldCount; i++)
            {
                Console.WriteLine("   {0} ", r[i]);
            }
        }
    }
}