c# - Linq查询结果到List集合

Question

我使用下面的代码从两个表中获取记录，但我想将结果放在一个列表中。我使用了下面的代码，但是出现了这个错误:

Cannot implicitly convert type System.Collections.Generic.List<AnonymousType#1> to System.Collections.Generic.List<QuickRoutes.DAL.Route>

public List<Route> GetAllForUser(Guid userId)
{
    // var result = new List<Route>();
    aspnetdbDataContext aspdb = new aspnetdbDataContext();
    List<Route> result  = (from r in aspdb.Routes
                where r.UserId == userId
                join t in aspdb.TrackPoints on r.RouteId equals t.RouteFK
                select t.TrackPointId,t.RouteFK,t.TrackTime,t.Longitude,t.Latitude,t.Elevation, r.SourceName).ToList();
    return result;
}

编辑:

我想将我的查询与此类匹配:

namespace QuickRoutes.Entities
{
    public enum RouteType
    {
        Route, Waypoints, Track
    }

    public sealed class Route
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public DateTime Time { get; set; }
        public List<TrackPoint> TrackPoints { get; set; }
        public Guid UserId { get; set; }
        public string GpxData { get; set; }
        public RouteType RouteType { get; set; }


        public Route(int id)
        {
            Id = id;
            TrackPoints = new List<TrackPoint>();
        }
......

但是如果我把我的代码改成这个，它也不起作用

List<Route> result = (from r in aspdb.RouteLinqs
                                  where r.UserId == userId
                                  join t in aspdb.TrackPointlinqs on r.RouteId equals t.RouteFK
                                  select r).ToList();

老实说，我想把这个用SQL写的函数改成LINQ，有什么更好的idea吗？

namespace QuickRoutes.Entities
{
    public enum RouteType
    {
        Route, Waypoints, Track
    }

    public sealed class Route
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public DateTime Time { get; set; }
        public List<TrackPoint> TrackPoints { get; set; }
        public Guid UserId { get; set; }
        public string GpxData { get; set; }
        public RouteType RouteType { get; set; }


        public Route(int id)
        {
            Id = id;
            TrackPoints = new List<TrackPoint>();
        }
......

Answer 1

这是因为您的投影(您选择的)与 Route 不同(您要返回的内容)；

如果您希望返回 Route将您的选择更改为:

select r

如果你想返回你的联合投影，你必须创建一个新类型，然后返回:

例如:

public class RouteTrack
{
    public TrackPointId ...
    public RouteFK ...
    public TrackTime ...
}

并返回 List<RouteTrack>从您的方法中，并将您的选择更改为:

select new RouteTrack { TrackPointId = t.TrackPointId .... }