How to use formulas from a XML file?

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Hi,

I have to store the Business logic into the XML, this would make it easy to change formulas once program is compiled.

For Example - f(x,y) = x+y or some complex operation - f(x,y) = (x + y - x/y) * (x-y) / 5

Posted 12-Mar-15 2:04am

anurag.netdeveloper

Updated 12-Mar-15 2:12am

RajeeshMenoth

v3

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nagendrathecoder 12-Mar-15 8:07am

So what's the problem? You can get examples for reading and writing to xml files from google.

2 solutions

Solution 1

Well the only build in solution that I can think of is the Microsoft Script Control Library. It can enable you to evaluate the expressions written in VBScript or JScript.
Note that it is a COM library and in order to use it you need to add reference to "Microsoft Script Control 1.0".

Here is how you would do this:

C#

private static string CalculateFormula(string formula, int x, int y)
{
    var controler = new MSScriptControl.ScriptControl();
    controler.Language = "VBScript";
 
    return controler.Eval(
        formula.Replace("x", x.ToString())
               .Replace("y", y.ToString())).ToString();
}

And here is an example of its usage:

C#

// Output: 15
Console.WriteLine(CalculateFormula("x+y", 12, 3));
// Output: 100
Console.WriteLine(CalculateFormula("(x + y - x/y) * (x-y) / 5", 25, 5));

If that does not suite you then you will need to look for some existing .NET formula evaluator, parser, engine or interpreter. You can find quite a few of them here on CodeProject.

Posted 12-Mar-15 3:22am

Mario Z

Updated 12-Mar-15 3:24am

v3

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Sergey Alexandrovich Kryukov · Accepted Answer · 2015-03-12T03:37:00

There is no any predefined concept of formula in XML. So, you can develop you own system with appropriate data schema and processing of expressions and so on. XML is no more then a media for storing data.

Basically, you have two major choices: unparsed expressions and parsed.

In unparsed approach, the expression can be any text content, and the software processing unit will take this text as is, no matter if it is valid or not. It may look like

HTML

<Expression>
   <Operands>
      <Operands>x</Operands>
      <Operands>y</Operands>
   </Operands>
   <Function>(x + y - x/y) * (x-y) / 5</Function>
</Expression>

In parsed approach, XML can represent the structure of expression.