按Linq结果集分组

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

public class SalesData
{
    public string Region { get; set; }
    public string Product { get; set; }
    public decimal SalesAmount { get; set; }
}

public class Program
{
    public static void Main()
    {
        List<SalesData> sales = new List<SalesData>
        {
            new SalesData { Region = "North", Product = "A", SalesAmount = 100 },
            new SalesData { Region = "North", Product = "B", SalesAmount = 200 },
            new SalesData { Region = "South", Product = "A", SalesAmount = 150 },
            new SalesData { Region = "South", Product = "B", SalesAmount = 250 }
        };

        var groupedByRegion = sales.GroupBy(s => s.Region);

        foreach (var group in groupedByRegion)
        {
            Console.WriteLine($"Region: {group.Key}");
            foreach (var item in group)
            {
                Console.WriteLine($"  Product: {item.Product}, SalesAmount: {item.SalesAmount}");
            }
        }

        var groupedByRegionAndProduct = sales.GroupBy(s => new { s.Region, s.Product });

        foreach (var group in groupedByRegionAndProduct)
        {
            Console.WriteLine($"Region: {group.Key.Region}, Product: {group.Key.Product}");
            foreach (var item in group)
            {
                Console.WriteLine($"  SalesAmount: {item.SalesAmount}");
            }
        }
    }
}