检查项目是否存在于字典中，并从C＃中的字典中删除它 [英] Check if an item exist in the dictionary and remove it from the dictionary in C#

问题描述

问题应该从标题本身清楚。我需要检查一个项目是否存在于字典中，并从C＃中的字典中删除它。唯一的办法是，我只能使用值项而不是键。

The question should be clear from the title itself. I need to check if an item exist in the dictionary and remove it from the dictionary in C#. The only catch is that i have to do this using only the value item and not the key.

声明如下：

IDictionary<string, myCustomClassObject> clients = new IDictionary<string, myCustomClassObject>();

现在我通过以下方式填写字典：

Now i fill in the dictionary by:

clients["key"] = myCustomClassObject1;

现在如何找到并删除此项 myCustomClassObject1 从我的词典。我只想使用值项目而不是键

Now how can i find and remove this item myCustomClassObject1 from my Dictionary. I only want to use the value item and not the key

这是doabale ...如果是这样，请指导...

Is this doabale...if so please guide... regards

编辑：谢谢大家....有价值的意见...可能有一些想法...感谢

Thank you all....got valuable comments...probably have some thinking to do ...thanks

推荐答案

这取决于你需要如何执行。如果您可以接受 O（N）的表现，您可以执行以下操作：

It depends on how you need it to perform. If you can accept O(N) performance, you could just do something like:

foreach(var pair in clients) {
    if(pair.Value == expected) {
        clients.Remove(pair.Key);
        break;
    }
}

然而，如果你需要更快，你需要两个字典 - 一个与另一个相反（即由实例锁定）。因此，添加时，您可以：

However, if you need faster you would need two dictionaries - one the reverse of the other (i.e. keyed by the instances). So when adding, you would do:

clientsByKey.Add(key, value);
clientsByValue.Add(value, key);

，以便您可以执行（按值移除）：

so you can do (to remove-by-value):

string key;
if(clientsByValue.TryGetValue(value, out key)) {
    clientsByValue.Remove(value);
    clientsByKey.Remove(key);
}

或类似（按键删除）：

Foo value;
if(clientsByKey.TryGetValue(key, out value)) {
    clientsByValue.Remove(value);
    clientsByKey.Remove(key);
}

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