Linq表达式如何确定平等？ [英] How do Linq Expressions determine equality?

问题描述

我正在考虑使用Linq Expression作为字典中的关键字。然而，我担心我会得到奇怪的结果，因为我不知道平等是如何由Linq表达式决定的。

I am considering using a Linq Expression as a key in a dictionary. However, I am concerned that I will get strange results, because I don't know how Equality is determined by Linq expressions.

派生自表达式的类比较值相等或引用相等吗？或者换句话说，

Does a class derived from Expression compare value equality or reference equality? Or in other words,

        Expression<Func<object>> first = () => new object(); 
        Expression<Func<object>> second = ()=>new object();
        bool AreTheyEqual = first == second;

推荐答案

您的测试比较表达式 。表达本身只提供参考平等;您的测试可能会显示假。例如，为了面对语义平等，你需要做很多工作，是：

Your test compares expressions. Expressions themselves offer only reference equality; your test will probably show "false". To cheek for semantic equality you would need to do a lot of work, for example - are:

x => 123

和

y => 123

等效？作为一个粗糙的测试，您可以比较ToString（），但这将是非常脆弱的。

Equivalent? As a crude test you can compare ToString(), but this will be exceptionally brittle.

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