在EX pression树木落实不，.NET 4 [英] Implement Not in expression trees, .net 4

问题描述

是否有可能实现！ （不）使用EX pression树。我感兴趣的创建，将分析和评估逻辑EX pressions含真，假，||，＆放一个C＃的eval类;＆安培;和 ！。我知道，与功放;＆安培;和||目前由.NET 4 EX pression树木的支持，但我想知道如果他们的是一种方法来实现类似summat！（X放大器;＆安培; Y）||当z =假，Y =真和z =假的。

Is it possible to implement a ! (not) using expression trees. I'm interested in creating a C# eval class which will parse and evaluate logical expressions which contain true, false, ||, && and !. I know that && and || are currently supported by .NET 4 expression trees, but I was wondering if their is a way to implement summat like !(x && y) || z where z=false, y=true and z=false.

目前我使用的是标准的基于堆栈的标记生成器，分析器，评估，以评估这些类型的EX pression，但会happly倾倒，如果有合适的EX pression树可以创建和动态执行

Currently I'm using a standard stack based tokenizer, parser, evaluator to evaluate these types of expression but would happly dump it, if a suitable expression tree could be created and executed on the fly.

推荐答案

我通常会发现，它的价值编码的lambda EX pression这确实是我想要的，然后看一下C＃编译器吧。

I usually find that it's worth coding a lambda expression which does what I want, and then seeing what the C# compiler does with it.

所以这个code：

Expression<Func<bool,bool>> func = x => !x;

被编译为：

ParameterExpression expression2;
Expression<Func<bool, bool>> expression = 
       Expression.Lambda<Func<bool, bool>>(Expression.Not(
            expression2 = Expression.Parameter(typeof(bool), "x")), 
                new ParameterExpression[] { expression2 });

（道歉格式 - 这是很难知道该怎么做与）

(Apologies for the formatting - it's hard to know what to do with that.)

这是反编译带反射，但它的优化设置为.NET 2.0，以避免使用lambda语法。

That's decompiled with Reflector, but with its "optimization" set at .NET 2.0 to avoid it using lambda syntax.

一旦你过去的垃圾，你会看到它使用<一个href="http://msdn.microsoft.com/en-us/library/system.linq.ex$p$pssions.ex$p$pssion.not.aspx"><$c$c>Ex$p$pssion.Not. ＆功放;＆安培;使用<一个href="http://msdn.microsoft.com/en-us/library/system.linq.ex$p$pssions.ex$p$pssion.andalso.aspx"><$c$c>Ex$p$pssion.AndAlso,和||使用<一个href="http://msdn.microsoft.com/en-us/library/system.linq.ex$p$pssions.ex$p$pssion.orelse.aspx"><$c$c>Ex$p$pssion.OrElse.

Once you've got past the junk, you'll see it's using Expression.Not. && uses Expression.AndAlso, and || uses Expression.OrElse.

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