如何通过内联代码对列表中的项目进行分组和拆分？

Question

我正在使用数据库。我想获取所有消息并根据<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script> <div ng-app="testApp" ng-controller="testCtrl"> <h1>{{print()}}</h1> </div>对它们进行分组（1个会话包含具有相同RoomId的消息）。

我试过这个：

RoomId

输出：

我想内联部分：

public class Message
{
    public string SenderId { get; set; }

    public string ReceiverId { get; set; }

    public string RoomId { get; set; }
}

class Program
{
    static void Main()
    {
        var list = new List<Message>
            {
                new Message { SenderId = "Sender1", ReceiverId = "Receiver1", RoomId = "Room2" },
                new Message { SenderId = "Sender1", ReceiverId = "Receiver1", RoomId = "Room1" },
                new Message { SenderId = "Sender1", ReceiverId = "Receiver1", RoomId = "Room3" },
                new Message { SenderId = "Sender1", ReceiverId = "Receiver1", RoomId = "Room1" },
                new Message { SenderId = "Sender1", ReceiverId = "Receiver1", RoomId = "Room2" },
                new Message { SenderId = "Sender1", ReceiverId = "Receiver1", RoomId = "Room3" }
            };

        var group_list = list.GroupBy(x => x.RoomId);

        var output_list = new List<List<Message>>();

        foreach (var item in group_list)
        {
            output_list.Add(item.ToList());
        }

        foreach (var item in output_list)
        {
            Console.WriteLine($"Conversation {output_list.IndexOf(item) + 1}");

            foreach (var msg in item)
            {
                Console.WriteLine($"SenderId: {msg.SenderId}\tReceiverId: {msg.ReceiverId}\tRoomId: {msg.RoomId}");
            }

            Console.WriteLine();
        }
    }
}

为：

foreach (var item in group_list)
{
    output_list.Add(item.ToList());
}

我该怎么做？

Answer 1

在GroupBy之后，您选择了IEnumerable<Message>的群组，因此您可以使用ToList：

List<List<Message>> output_list = list
    .GroupBy(x => x.RoomId)
    .Select(g => g.ToList())
    .ToList();