比较两个集合 [英] Comparing two collections

问题描述

我有什么看起来像一个常见的问题/模式。两个集合相同的对象。该对象具有许多属性和其中的一些嵌套对象。 Car有一个名为id的属性，它是唯一的标识符。

i have what seems like a common problem / pattern. two collections of the same object. The object has a number of properties and some nested objects within it. Car has a property called id which is the unique identifier.

我想找到LINQ的方式来做一个diff，其中包括：

I want to find the LINQ way to do a diff, which includes:

1. 一个集合中的项目，而不是另一个集合中的项目（反之亦然）


2. 对于匹配的项目，是否有任何更改（我只关心可设置的属性，我会使用反射吗？）

推荐答案

您可以使用 Enumerable.Except（）方法，使用比较器（默认值或您提供的值）来评估哪些对象两个序列或只有一个：

You can use the Enumerable.Except() method. This uses a comparer (either a default or one you supply) to evaluate which objects are in both sequences or just one:

var sequenceA = new[] { "a", "e", "i", "o", "u" };
var sequenceB = new[] { "a", "b", "c" };

var sequenceDiff = sequenceA.Except( sequenceB );

如果要执行两个序列的完全析取 （BA），您必须使用：

If you want to perform a complete disjunction of both sequences (A-B) union (B-A), you would have to use:

var sequenceDiff = 
         sequenceA.Except( sequenceB ).Union( sequenceB.Except( sequenceA ) );

如果你有一个复杂的类型，你可以写一个 IComparer< T&

If you have a complex type, you can write an IComparer<T> for your type T and use the overload that accepts the comparer.

对于您的问题的第二部分，您需要滚动您自己的实现来报告类型的哪些属性是不同的..没有内置到.NET BCL直接。您必须决定此报告将采用什么形式？你如何识别和表达复杂类型的差异？你可以使用反射这个...但如果你只处理一个类型，我会避免，并写一个专门的差异实用程序只为它。如果你要支持一系列的类型，反射可能会更有意义。

For the second part of your question, you would need to roll your own implementation to report which properties of a type are different .. there's nothing built into the .NET BCL directly. You have to decide what form this reporting would take? How would you identify and express differences in a complex type? You could certainly use reflection for this ... but if you're only dealing with a single type I would avoid that, and write a specialized differencing utility just for it. If yo're going to support a borad range of types, then reflection may make more sense.

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