Question

我想创建一个程序来读取文本文件（书名），并将每个书名对应一个用户评级。我如何为阵列中的书名分配多个评级？

到目前为止，我有，

class Program
{
    static void Main(string[] args)
    {
        string[] lines = File.ReadAllLines("books.txt");

    }

用户评级位于此表单的单独文本文件中：

User:a
2 
5 
4 
1
1
User:b
5
5
0
1
2

如果有5本书和2位用户，我如何将2和5的分数与一本名为“饥饿游戏玩家”的书联系起来？

Answer 1

这里似乎有3个数据：书籍，用户和评级。你可以为每一个创建结构并用适当的数据填充它们，然后你可以用它们做各种有趣的事情。

以下是一个例子：

public class Book
{
    public int ID;
    public string Name;
}

public class User
{
    public int ID;
    public string Name;
}

public class Rating
{
    public int UserID;
    public int BookID;
    public int Value;
}

从基本级别开始，您可以将这些项目的列表加载到数组中：

Book[] books = new Book[] 
    { 
        new Book { ID = 1, Name = "A B C" },
        new Book { ID = 2, Name = "Word Two" },
        new Book { ID = 3, Name = "Third Book" },
        new Book { ID = 4, Name = "And Another" },
        new Book { ID = 5, Name = "The Last Word" }
    };

User[] users = new User[] 
    { 
        new User { ID = 1, Name = "A" },
        new User { ID = 2, Name = "B" },
    };

Rating[] ratings = new Rating[] 
    {
        new Rating { UserID = 1, BookID = 1, Value = 2 },
        new Rating { UserID = 1, BookID = 2, Value = 5 },
        new Rating { UserID = 1, BookID = 3, Value = 4 },
        new Rating { UserID = 1, BookID = 4, Value = 1 },
        //new Rating { UserID = 1, BookID = 5, Value = 1 },
        new Rating { UserID = 2, BookID = 1, Value = 5 },
        new Rating { UserID = 2, BookID = 2, Value = 5 },
        new Rating { UserID = 2, BookID = 3, Value = 0 },
        new Rating { UserID = 2, BookID = 4, Value = 1 },
        //new Rating { UserID = 2, BookID = 5, Value = 2 },
    };

现在为了一些有趣的事情......

您收藏集中所有图书的平均评分列表（包括没有评分的图书，我在ratings初始化程序中评论的图书）：

var bookRatings = 
// start with books
    from bk in books
// get all the ratings related to each book...
    join r in ratings on bk.ID equals r.BookID into _ratings
// put a default value (null, no value) when no ratings were found
    from r in _ratings.DefaultIfEmpty()
// now group the ratings by book
    group (r == null ? null : (int?)r.Value) by bk into grp
// and now do some calculations:
    select new 
        {
            grp.Key.ID,
            grp.Key.Name,
            Rating = grp.Average(),
            NumRatings = grp.Count(v => v != null)
        };

// Now display it:
foreach (var result in bookRatings)
    Console.WriteLine("{0}\t{1,-15}\t{2}\t{3}", result.ID, result.Name, result.Rating, result.NumRatings);

这是输出：

1   A B C           3.5 2
2   Word Two        5   2
3   Third Book      2   2
4   And Another     1   2
5   The Last Word       0

我已经使用了classes，arrays，anonymous types以及一些相当有趣的LINQ表格，但这些都是很好的学习内容。点击链接并进行一些阅读，直到您了解上面发生的大部分内容为止。

顺便提一下，如果我将数据存储在数据库中，上面几乎就是我要做的事情 - 整体结构相同，几乎相同的代码。转换时，LINQ to SQL消除了很多实施的痛苦。

Answer 2

您可以在此处使用Dictionary。喜欢这个

Dictionary<string, List<int>> bookMapping = new Dictionary<string, List<int>>();
bookMapping.Add("youruserkey", new List<int> { 1, 2, 3, 4, 5 });

PS：请详细阅读链接的详细信息。

如何将数组中的元素引用到多个其他值？

2 个答案: