如何在Asp.Net Mvc中创建一个向用户返回建议列表的方法？ [英] How Do I Create A Method In Asp.Net Mvc That Returns A List Of Recommendations To The User?

问题描述

我创建了db和tables以及每个表的模型类，它们具有与列名相同的属性。如何在控制器类[Asp.Net MVC]中创建一个方法，以向用户返回音乐推荐列表，即用户朋友库中的音乐。每个用户的库中都有一个音乐曲目列表，每个用户都有一个朋友列表（用户）。建议是所有音乐曲目，由用户的直接朋友拥有，但不由用户拥有。使用MusicInfoDBContext类和Dbsets类似：public DbSet< Users>用户{get;组;以下是该方法的签名：

I have created the db and tables and a model classes of each table having the same properties as column name. How do i create a method in controller class [Asp.Net MVC] to return a list of recommendation of music to the user i.e the musics that are in the library of users friends. Each user has a list of music tracks in their library and each user has a list of friends(Users). Recommendations are all the music tracks, which are owned by the user’s immediate friends but not by the user. Similary using a MusicInfoDBContext class and Dbsets: public DbSet<Users> Users{ get; set; } Following is the signature of the method:

List<Music> getMusicRecommendations(User user)
and the DBScript is as follows:


CREATE DATABASE OnlineMusicStore
  CREATE TABLE Users(
    ID int primary key identity(1,1),
    Username nvarchar(255)
    )

    CREATE TABLE Music
    (
    ID int primary key identity(1,1),
    MusicName nvarchar(255),
    )

    CREATE TABLE Users_Music
    (
    UserId int foreign key references Users(ID),
    MusicId int foreign key references Music(ID)
    )

    CREATE TABLE Users_Friends
    (
    UserId int foreign key references Users(ID),
    FriendId int foreign key references Users(ID)
    )
 public class Users
    {
        public int ID { get; set; }
        public string UserName { get; set; }
    }
  public class Music
    {
        public int ID { get; set; }
        public string MusicName { get; set; }
    }
 public class Users_Music
    {
        public int UserId { get; set; }
        public int MusicId { get; set; }
    }
  public class Users_Friends
    {
        public int UserId { get; set; }
        public int FriendId { get; set; }
    }

任何人都可以详细说明解决方案，因为我可以更好地理解它。我的一位朋友建议使用：

Can anyone elaborate the solution as i can understand it better. One of my Friend suggested using:

recommendations = AllFriendsMusicList.Except(user.MusicList);

推荐答案

您需要从User_Music表中选择所有记录，除了当前Userid的音乐和同一用户的friends表中的所有用户。



假设您正在为用户UserId = 1寻找音乐推荐，那么查询应该像

You need to select all records from User_Music table except musics for the current Userid and all users that are in the friends table for the same user.

Suppose if you are looking for music recommendations for a user UserId = 1 then the query should be like

Select * from User_Music
where UserId <> @UserId and UserId in (Select FriendId from Users_Friends where UserId = @UserId)

希望这有帮助！

Hope this helps!

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