Dictionary.ContainsKey永远找不到密钥（使用集合初始化程序） [英] Dictionary.ContainsKey never finds a key (using a collection Initializer)

问题描述

我有一个带有intilizer集合的字典。我想将它用作我的密钥，但是当我进行检查时，它从未在我的dic MAP_ALARMS中找到它们。为什么？我的代码有什么问题？我还尝试将AlarmMapped对象首先存储在

 List< AlamrMapped>中。 mapList 

然后用作我的字典mapList [0]，mapList [1]的键。但是，它仍然没有找到任何键匹配。问题是什么？

< pre lang =cs> public class AlarmMapped
{
public string SubsystemId { get ; set ; }
public string 代码{ get ; set ; }
public string SystemId { get ; set ; }
public AlarmMapped（ string systemId， string subsystemId， string subsystemCode）
{
SystemId = systemId;
SubsystemId = subsystemId;
Code = subsystemCode;
}
}

public 字典< AlarmMapped，字符串> MAP_ALARMS = new 字典< AlarmMapped，字符串>（）
{
{ new AlarmMapped（ SYSTEM_STERRING， < span class =code-string> SUBSYSTEM_STERRING_POWERUNIT， 004），< span class =code-string> Phase Fail}，
{ new AlarmMapped（ SYSTEM_STERRING， SUBSYSTEM_STERRING_POWERUNIT， 005 ）， 液压油液位}，

};

public void myFunction（）{

CheckMap（ new AlarmMapped（ SYSTEM_STERRING ， SUBSYSTEM_STERRING_POWERUNIT， 005）;
}

public void CheckMap（AlarmMapped m）{

if （MAP_ALARMS.ContainsKey（m））{

......
}
}

解决方案

您正在比较引用对象（对于不同的对象，它们不能相等，即使它们包含相同的数据）。

见这里：比较用作词典中键的对象 [ ^ ]。

嗯。

AlarmMapped是一个类，这意味着你的Dictionary包含对类实例的引用和对a的引用。字符串。

因此，对字典键进行检查以查找matych将比较类引用，而不是类内容。

因此，如果您的字典包含以下元素：

  public 字典< AlarmMapped，string> MAP_ALARMS =  new 字典< AlarmMapped，字符串>（）
 {
 { new  AlarmMapped（  SYSTEM_STERRING， < span class =code-string> SUBSYSTEM_STERRING_POWERUNIT，  004），< span class =code-string>  Phase Fail}，
 { new  AlarmMapped（  SYSTEM_STERRING，  SUBSYSTEM_STERRING_POWERUNIT，  005 ）， 液压油液位}，
 
}; 

然后你针对你班级的新实例进行检查：

 CheckMap（ new  AlarmMapped（  SYSTEM_STERRING，  SUBSYSTEM_STERRING_POWERUNIT，   005）; 

您将检查是否有新实例引用存在于字典中 - 根据定义它不会，因为它是 new 实例，即使它包含相同的数据。



这就像把你的手机放在你的办公桌抽屉里，然后期望在你的办公桌抽屉里找到的手机中找到你的联系人和信息！

I have a dictionary with a intilizer collection. I want to use that as my key but it never founds them in my dic MAP_ALARMS when I do the check. Why? what is wrong in my code? I also tried storing first the AlarmMapped objcts in a

List<AlamrMapped> mapList

and then use as keys of my dictionary mapList[0],mapList[1].. but still , it never finds any key matching.Whats the problem?

public class AlarmMapped
    {
        public string SubsystemId { get; set; }
        public string Code { get; set; }
        public string SystemId { get; set; }
        public AlarmMapped(string systemId, string subsystemId, string subsystemCode)
        {
            SystemId = systemId;
            SubsystemId = subsystemId;
            Code = subsystemCode;
        }
}

public Dictionary<AlarmMapped, string> MAP_ALARMS = new Dictionary<AlarmMapped, string>()
       {
        {  new AlarmMapped ("SYSTEM_STERRING","SUBSYSTEM_STERRING_POWERUNIT","004"),"Phase Fail"},
        {  new AlarmMapped ("SYSTEM_STERRING","SUBSYSTEM_STERRING_POWERUNIT","005"),"Hydraulic fluid level"},

       };

public void myFunction(){

CheckMap(new AlarmMapped("SYSTEM_STERRING","SUBSYSTEM_STERRING_POWERUNIT","005");
}

public void CheckMap(AlarmMapped m){

if(MAP_ALARMS.ContainsKey(m)){

......
}
}

解决方案

You are comparing references to objects (they cannot be equal for differenct objects, even if they contain same data).
See here: "Comparing object used as Key in Dictionary"[^].

Um.
AlarmMapped is a class, which means that your Dictionary consists of a reference to a class instance, and a reference to a string.
So any checking against the dictionary keys to find a matych will compare class references, not class content.
So if your dictionary contains these elements:

public Dictionary<AlarmMapped, string> MAP_ALARMS = new Dictionary<AlarmMapped, string>()
       {
        {  new AlarmMapped ("SYSTEM_STERRING","SUBSYSTEM_STERRING_POWERUNIT","004"),"Phase Fail"},
        {  new AlarmMapped ("SYSTEM_STERRING","SUBSYSTEM_STERRING_POWERUNIT","005"),"Hydraulic fluid level"},

       };

And you check it against a new instance of your class:

CheckMap(new AlarmMapped("SYSTEM_STERRING","SUBSYSTEM_STERRING_POWERUNIT","005");

you will be checking to see if the new instance reference exists in the dictionary - which by definition it won't because it is a new instance, even if it contains the same data.

It's like putting your mobile phone in your desk drawer, and then expecting to find your contacts and messages in a phone you found in my desk drawer!

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