Question

我有一个火车数据库，其中包含所有必填字段，例如火车，路线，车站，乘客，预订等。我想使用LINQ在一对车站之间获得火车（我知道SQL查询，但是我无法将其转换为LINQ）。请任何人帮助我。

还有一件事情，我想要LINQ查询的 Extension方法方法（不是像from，in，select 这样的关键字），例如

var trains = _context.Trains.FirstOrDefault(a => a.Id == text);

SQL查询

SELECT Route.TrainId, Train.TrainName 
FROM Route 
INNER JOIN Train ON Route.TrainId=Train.TrainId 
WHERE 
    (Route.StationId IN 
        (SELECT Source.StationId 
         FROM Route AS Source 
         INNER JOIN Route AS Destination ON Source.TrainId=Destination.TrainId 
         WHERE 
             (Source.StopNumber - Destination.StopNumber < 0) 
              AND 
             (Source.StationId = @Source) 
              AND
             (Destination.StationId = @Destination)
         )
     )

如果您想要更多详细信息，例如表结构，请评论我。我从在线幻灯片中获得了表结构和查询。

Answer 1

我使用类对数据库进行建模。试试这样的东西

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Train> trains = new List<Train>();
            string source = "abc";
            string destination = "xyz";


            var results = trains.Where(x => x.Routes.Any(y => y.StationId == source) && x.Routes.Any(y => y.StationId == destination))
                .Select(x => new {
                    source = x.Routes.Where(y => y.StationId == source).FirstOrDefault(),
                    destination = x.Routes.Where(y => y.StationId == destination).FirstOrDefault()
                })
                .Where(x => x.destination.StopNumber > x.source.StopNumber)
                .ToList();
        }
    }
    public class Train
    {
        public string TrainName { get; set; }
        public List<Route> Routes { get; set; }
    }
    public class Route
    {
        public string TrainId { get; set; }
        public string StationId { get; set; }
        public int StopNumber { get; set; }
    }
}

火车数据库中的linq查询

1 个答案: