执行表连接后在C#中处理lambda查询结果

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

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class Order
{
    public int PersonId { get; set; }
    public decimal Amount { get; set; }
}

public class Program
{
    public static void Main()
    {
        List<Person> people = new List<Person>
        {
            new Person { Id = 1, Name = "Alice" },
            new Person { Id = 2, Name = "Bob" }
        };

        List<Order> orders = new List<Order>
        {
            new Order { PersonId = 1, Amount = 100 },
            new Order { PersonId = 1, Amount = 200 },
            new Order { PersonId = 2, Amount = 150 }
        };

        // 使用LINQ进行内连接
        var queryResult = from person in people
                          join order in orders on person.Id equals order.PersonId
                          select new { person.Name, order.Amount };

        foreach (var item in queryResult)
        {
            Console.WriteLine($"Name: {item.Name}, Amount: {item.Amount}");
        }
    }
}

// 修改查询为分组求和
var totalAmountPerPerson = from person in people
                           join order in orders on person.Id equals order.PersonId
                           group new { person, order } by person.Id into g
                           select new { PersonId = g.Key, TotalAmount = g.Sum(x => x.order.Amount) };

foreach (var item in totalAmountPerPerson)
{
    Console.WriteLine($"PersonId: {item.PersonId}, TotalAmount: {item.TotalAmount}");
}