动态if语句评估/生成 [英] Dynamic if statement evaluation/generation

问题描述

大家好，

我想评估动态if语句，例如下面的

Hello everyone,

I want to evaluate dynamic if statement like the e.g below

int a=2;
String condition="a==2";

if(condition)
execute something
else
execute something

我的意思是条件是可变的，它来自数据库.
例如:

I mean that the condition is changeable, and it''s coming from database.
For example:

String condition="";
int a, b, c, d;

....
条件可能是:

....
The condition could be:

condition = "a == 2";

或可能是:

or could be:

condition = "a >= b && c == a && ((d - 4) == a ) ";

或

or

condition = ".....something else......";

if(condition)
execute something
else
execute something

条件不是恒定的.那是我的问题.

我该怎么做...请让我知道.
在此先感谢

[修改:只是将代码标记更改为前置标记...以这种方式更易于阅读IMO]

The condition is not constant. That''s my problem.

How i can do this... Please let me know..
Thanks in advance

[Modified: just changed the code tags to pre tags...a bit easier to read that way IMO]

推荐答案

使用内置的.NET框架可能会在代码编译器中.我从来没有自己做过，但是我已经看过用IronRuby等做过的演示.诚然，它们是动态语言，但是应该可以用C#来做.

此 [此处 [

It might be possible using the .NET framework built in code compiler. I have never done this myself, but i have seen demos of it done with IronRuby, etc. Admittedly they were dynamic languages, but should be possible to do it in C#.

This[^] article on CodeProject might help.

There is also a calculator example here[^].

If the user is able to enter the a ==2 etc, you will have to be very careful checking input to make sure they don''t do anything nasty. Not sure how you would go about doing this.

您需要编写一个表达式评估器，该评估器可以接收字符串，解析字符串并使用变量评估数学表达式.没有内置功能可以执行此操作，因此您需要编写自己的代码或搜索第三方实现.

You need to write an expression evaluator that can take a string, parse it, and evaluate a mathematical expression with variables. There''s nothing built-in that can do this, so you need to write your own or search for a 3rd party implementation.

对于您的问题，我不太清楚.

以下代码(C#)有什么问题:

I am not very clear about your question.

What''s the problem with the below code (C#):

int a = 2;
if (a == 2)
{
    //execute something
}
else
{
    //execute something else
}

那么，通过评估动态if语句意味着什么?

And what do you mean by evaluating dynamic if statement?

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