C#: How to create and use a database of equations?

Question

I've been trying to create a database of equations that my windows form application will supply variables to and then calculate the solution. I was trying to store my equations in a text file and load them into a list but I haven't been able to think of how to translate my equation from a string to an actual equation.

So, does anyone know how I could store and call on a collection of equations that use variables from my windows form application.

P.S. Please keep it simple or explain thing fully. I get confused easily.

https://www.google.com/search?q=eval+function+c%23. I assume that the users of your application will be creating custom equations, yes? If not, just create the equations in code. — Robert Harvey, Jul 11 '12 at 15:17
You are indeed correct that there will be custom equations being created. — matt pruent, Jul 11 '12 at 15:34

score 2 · Accepted Answer · edited May 23 '17 at 11:56

2

Your best bet is to use a math library to evaluate your math expressions.

Here are some links to get you started: https://stackoverflow.com/questions/1387430/recommended-math-library-for-c-net

You can also take a look in http://ncalc.codeplex.com/ that may be exaclty what you want.

edited May 23 '17 at 11:56

Community

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answered Jul 11 '12 at 15:23

Ricardo Souza

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NCalc is a good suggestion; I suspect most math libraries lack the necessary parser. – Robert Harvey Jul 11 '12 at 15:39
I will give this a look. I hope its easy to use. – matt pruent Jul 11 '12 at 15:44
NCalc does look like what I need but I dont know how to add it. Im using Microsoft Visual C# 2010 Express. Any suggestions? – matt pruent Jul 11 '12 at 15:52
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You can download the assembly and add as a reference (rightclick on references folder > Add reference > Browse) – Ricardo Souza Jul 11 '12 at 17:06
Figured out how to add the library on my own but Im worried this is a bit over my head. – matt pruent Jul 11 '12 at 17:12
You will get used to it. Just follow the tuts in the site and you will be good to go. – Ricardo Souza Jul 11 '12 at 18:04

score 0 · Answer 2 · answered Jul 11 '12 at 17:53

You can do this using dynamic SQL. Here is how in SQL Server.

You can store the equation in a table, along with the variables that it needs (or if you have a fixed set of variables, that's fine).

Fetch the equation into a C# string.

Then construct the following statement:

select <equation>
from (select <val1> as variable1, <val2> as variable2) t

Where you put in the equation where is and the values of the variables where the values are.

Execute this statement in the database. Voila! The result will be the result of the equation.

There are some downsides to this approach. It requires two round trips to the database (one to get the equation and the other to run the equation). You are also limited to the functionality of the database. Also, if you are not using SQL Server, the syntax could be different (for instance, in Oracle, the inner subquery would have "from dual" in it).

C#: How to create and use a database of equations?

2 Answers2