如何评估(数学)字符串表达式，vb.net [英] how to evaluate ( math ) a string expression, vb.net

问题描述

我不确定我使用的术语是否正确.但我有一个字符串表达式，我想计算它.这是一个例子

I'm not sure the term I used is correct. but I have a string expression and I want it to be calculated. this an example

Dim S = "4+4"
dim result = evaluate(S) 'some sort of treatment // that return 8

我不确定这将如何运作.我熟悉 JS eval 函数.但似乎我需要添加某种图书馆.我不想那样做.我找到了一些关于使用

I'm not sure how this is going to work. I'm familiar with the JS eval function. but it seems that I need to add some sort of a library. and I don't want to do that. I have found some links about using

dim s = new expression("4+4") 

并使用

s.evaluate()

但这需要添加另一个库.正如我之前所说，我不想使用任何图书馆.我只想要一个如何进行的解决方案?我撞墙了.顺便说一句，我仍然是初学者，请尽量回答简单，我将不胜感激.

but that require to add another library. and as I said before I don't want to use any library. I just want a solution on how to proceed? I have hit a wall. BTW I'm still a beginner try to answer as simple as you can I would appreciate it.

推荐答案

您可以使用 DataTable.Compute-技巧":

You can use the DataTable.Compute-"trick":

Dim tbl = new DataTable()
Dim result = Convert.ToDouble(tbl.Compute("4+4", Nothing))

表达式支持以下算术运算符:

The following arithmetic operators are supported in expressions:

+ (addition)
- (subtraction)
* (multiplication)
/ (division)
% (modulus)

更多信息:DataColumn.Expression 在表达式语法.

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