如何在LINQ中组合对象的属性中的列表？

// 主对象集合
List<MainObject> mainObjects = new List<MainObject>
{
    new MainObject { Id = 1, Name = "Object 1", SubObjectIds = new List<int> { 1, 2, 3 } },
    new MainObject { Id = 2, Name = "Object 2", SubObjectIds = new List<int> { 4, 5 } },
    new MainObject { Id = 3, Name = "Object 3", SubObjectIds = new List<int> { 6 } }
};

// 子对象集合
List<SubObject> subObjects = new List<SubObject>
{
    new SubObject { Id = 1, Name = "SubObject 1" },
    new SubObject { Id = 2, Name = "SubObject 2" },
    new SubObject { Id = 3, Name = "SubObject 3" },
    new SubObject { Id = 4, Name = "SubObject 4" },
    new SubObject { Id = 5, Name = "SubObject 5" },
    new SubObject { Id = 6, Name = "SubObject 6" }
};

// 使用Join和SelectMany进行组合
var combinedList = mainObjects
    .Join(subObjects, main => main.SubObjectIds, sub => sub.Id, (main, sub) => new { Main = main, Sub = sub })
    .SelectMany(x => x.Main.SubObjectIds.Select(id => new { Main = x.Main, Sub = subObjects.FirstOrDefault(s => s.Id == id) }));

// 遍历组合后的结果
foreach (var item in combinedList)
{
    Console.WriteLine($"Main Object: {item.Main.Name}, Sub Object: {item.Sub.Name}");
}