类实例的C#字典 [英] C# dictionary of class instances

问题描述

你好

我正在创建一个音乐播放器.
我有这个课:

Hello

I am creating a music player.
I have this class:

class Song
    {
        internal int length { get; set; } //the length of the song 
        internal string FullPath { get; private set; } //full path like C:\\Music\song.mp3
        internal string Directory { get; private set; } //e.g C:\\Music
        internal string Name { get; private set; } // e.g song.mp3
        public Song(string path)
        {
            FullPath = path;
            Directory = System.IO.Path.GetDirectoryName(path);
            Name = System.IO.Path.GetFileNameWithoutExtension(path);
        }
    }

我还有一个字典，其中包含用户输入的每首歌曲的此类的所有实例.

我正在寻找一种检索

I also have a dictionary which holds all the instances of this class for each song which the user inputs.

I am looking for a way to retrieve the

int length

只需使用歌曲名...就可以从字典中存储的"Song"类的任何实例中获取歌曲. 我检索歌曲名称的方法是获取我正在使用的Windows Media Player控件的URL.
所以我正在寻找这样的东西

from any instance of the class ''Song'' stored in the dictionary just by using the song name...
The way I retrieve the song name is by getting the URL of the Windows Media Player control I''m using..

so I am looking for something like this

int x = Dictionary[wmp.URL.ToString()].length 

(我知道代码将无法工作，但我只是想对自己的要求有所了解)

我真的希望有人能够理解我的要求并提供帮助:)

(I know that code will not work but I just wanted to give an idea of what I was asking)

I really hope there is someone who can understand what I''m asking and can help :)

推荐答案

首先，System.Collections.Generic.Dictionary<TKey, TValue>具有两个通用参数，而不是一.访问是通过键完成的，因此您需要键的类型和值的类型.密钥应该是唯一的.它是什么?说，这首歌的完整标题，然后是一个字符串.如果不是，则可能是标题，首次发行年份和作者姓名的组合.在这种情况下，您需要一个键的类或结构.另外，您还需要使用键GetHashCode覆盖键类型中的等价/身份方法.如果您覆盖System.Object.Equals，则实际上正式需要哈希码覆盖，并且该键实际上由键/值关联的容器使用.

请参阅:
http://msdn.microsoft.com/en-us/library/system.object.aspx [ ^ ]，
http://msdn.microsoft.com/en-us/library/xfhwa508.aspx [ ^ ].

一个较小的问题是多余的Directory和Name(您的解释中的文件名).这只是一个设计错误(请参阅: http://en.wikipedia.org/wiki/Don%27t_repeat_yourself [ ^ ]).这样，可以创建相互矛盾的实例.永远不要做这样的事情.说，引入全路径FileName；但是您还可以具有文件名和目录的属性，但是可以基于全名和使用System.IO.Path方法即时返回值.

—SA

First of all, System.Collections.Generic.Dictionary<TKey, TValue> has two generic parameters, not one. The access is done via the keys, so you need a type for a key and a type for a value. The key should be unique. What is it? Say, the full title of the song, then a string. If not, it could be a combination of the title, the year of first release and the names of the authors. In this case, you need a class or a structure of the keys. Also, you need to override the equivalence/identity methods in the key type with its GetHashCode; the hash code override is actually formally required if you override System.Object.Equals and is actually used by key/value associated containers.

Please see:
http://msdn.microsoft.com/en-us/library/system.object.aspx[^],
http://msdn.microsoft.com/en-us/library/xfhwa508.aspx[^].

One minor problem is redundant Directory and Name (file name in your interpretation). This is just a design bug (please see: http://en.wikipedia.org/wiki/Don%27t_repeat_yourself[^]). In this way, it''s possible to create instances contradicting to each other. Never do such things. Say, introduce a full-path FileName; but you can also have properties for file name and directory, but returning values on the fly based on full name and the use of System.IO.Path methods.

—SA

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