Question

我可能会对这个问题有所了解，但我在这里找不到我的错误，我很乐意提供帮助。

问题是我的List<string> names电影名称应与db.MovieModels中的名称相同，但每次item都与name相同c我的db.MovieModels中的c应与db.MovieModels匹配，但未被选中。所以我的查询保持空白。

我的linq搜索有问题吗？

（item = "Pulp Fiction"包含电影，我可以看到断点，示例"Pulp Fiction"和电影中的电影名为public static ListModel CreateLists(string name, DateTime date, List<string> names) { ObservableCollection<MovieModel> contained = new ObservableCollection<MovieModel>(); // checks if the Movie Names from "names" are in the db foreach (var item in names) { var query = from c in db.MovieModels where c.Name == item select c; foreach (var t in query) { contained.Add(t); } } ListModel a = new ListModel { ListName = name, DateOfCreation = date.Date, MoviesList = contained }; return a; }，但仍然是空查询。）

CreateLists("Top 10 Rated - The Top Ten", new DateTime(2017, 5, 11), new List<string>
                {
                "The Godfather",
                "Forrest Gump",
                "The Shawshank Redemption",
                "The Dark Knight",
                "The Lord of the Rings: The Return of the King",
                "Star Wars: Episode V - The Empire Strikes Back",
                "Pulp Fiction",
                "Titanic",
                "Saving Private Ryan",
                "Star Wars: Episode IV - A New Hope",
                }));

编辑：好像我忘了方法的其余部分

EDIT2：看看如何使用该方法。

<MovieModel>

Edit3：

3 BP的图片。

Edit4：

我为db.MovieModels中的每个Name运行循环，并将它们与'列表名称'进行比较，什么都没有！

我正在使用SQLite，我经常使用MovieModels中的SharedPreferences sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);，所以我不明白为什么它不起作用。

Answer 1

为了找到匹配的MovieModel，您可以通过调用ToList来声明以下查询并请求它执行：

var matchedMovieModels = (from movieModel in db.MovieModels
                         join name in names                             
                         on movieModel.Name equals name
                         select movieModel).ToList();

这样做只需要往返数据库一次！虽然循环遍历names并且每个name试图找到哪些MovieModel可以匹配，但您可以像names.Length那样多次往返数据库。

<强>更新

public static ListModel CreateLists(string name, DateTime date, List<string> names)
{
    var matchedMovieModels = from movieModel in db.MovieModels
                             join name in names
                             on movieModel.Name equals name
                             select movieModel;
    return new ListModel
    {
        ListName = name,
        DateOfCreation = date.Date,
        MoviesList = new ObservableCollection<MovieModel>(matchedMovieModels)
    };
}

Answer 2

它似乎适用于此代码

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            ObservableCollection<MovieModel> models = CreateLists("a", DateTime.Now, new List<string>() { "a", "c" });
        }
        public static ObservableCollection<MovieModel> CreateLists(string name, DateTime date, List<string> names)
        {
            MovieModel db = new MovieModel() { 
                MovieModels = new List<MovieModel>() {
                    new MovieModel() { Name ="a"},
                    new MovieModel() { Name ="b"},
                    new MovieModel() { Name ="c"}
                }
            };

            ObservableCollection<MovieModel> contained = new ObservableCollection<MovieModel>();
            // checks if the Movie Names from "names" are in the db
            foreach (var item in names)
            {
                var query = from c in db.MovieModels
                            where c.Name == item 
                            select c;
                foreach (var t in query)
                {
                    contained.Add(t);
                }
            }

            return contained;
        }
    }
    public class MovieModel
    {
        public List<MovieModel> MovieModels { get; set; }

        public string Name { get; set; }

    }

}

UWP C＃失败了linq搜索

2 个答案: