如何在C#中比较两个字典 [英] How to compare two Dictionaries in C#

问题描述

我有两个通用词典.两者具有相同的键，但它们的值可以不同.我想比较第二本字典和第一本字典.如果它们的值之间存在差异，我想将这些值存储在单独的字典中.

I have two generic Dictionaries. Both have the same keys, but their values can be different. I want to compare the 2nd dictionary with the 1st dictionary. If there are differences between their values, I want to store those values in a separate dictionary.

1st Dictionary
------------
key       Value

Barcode   1234566666
Price     20.00


2nd Dictionary
--------------
key       Value

Barcode   1234566666
Price     40.00


3rd Dictionary
--------------
key       Value

Price     40

谁能给我最好的算法来做到这一点?我写了一个算法，但它有很多循环.我正在寻找一个简短而有效的想法，例如使用 LINQ 查询表达式或 LINQ lambda 表达式的解决方案.我在 C# 中使用 .NET Framework 3.5.我发现了一些关于 Except() 方法的信息，但不幸的是我无法理解该方法发生了什么.如果有人可以解释建议的算法，那就太好了.

Can anyone give me the best algorithm to do this? I wrote an algorithm but it has a lot of loops. I am seeking a short and efficient idea, like a solution using LINQ query expressions or LINQ lambda expressions. I am using .NET Framework 3.5 with C#. I found something about the Except() method, but unfortunately I couldn't understand what is happening on that method. It would be great if anyone could explain the suggested algorithm.

推荐答案

如果您已经检查过密钥是否相同，则可以使用:

If you've already checked that the keys are the same, you can just use:

var dict3 = dict2.Where(entry => dict1[entry.Key] != entry.Value)
                 .ToDictionary(entry => entry.Key, entry => entry.Value);

解释一下，这将:

• 迭代dict2
中的键/值对
• 对于每个条目，在 dict1 中查找值并过滤掉任何两个值相同的条目
• 通过从每一对中取出键和值，就像它们出现在 dict2 中一样，从剩余的条目(即 dict1 值不同的条目)形成一个字典.

• Iterate over the key/value pairs in dict2
• For each entry, look up the value in dict1 and filter out any entries where the two values are the same
• Form a dictionary from the remaining entries (i.e. the ones where the dict1 value is different) by taking the key and value from each pair just as they appear in dict2.

请注意，这避免了依赖 KeyValuePair - 依赖它可能没问题，但我个人觉得这更清楚.(当您为字典键使用自定义相等比较器时，它也可以工作 - 尽管您也需要将其传递给 ToDictionary.)

Note that this avoids relying on the equality of KeyValuePair<TKey, TValue> - it might be okay to rely on that, but personally I find this clearer. (It will also work when you're using a custom equality comparer for the dictionary keys - although you'd need to pass that to ToDictionary, too.)

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