Dynamic C# Formula Evaluation

Question

Given a dynamic if statement in a String is there a method in .net to evaluate and return the correct result.

I.E.

    static void Main(string[] args)
    {
        String a = "if(\"Alex\" == \"Alex\"){return 1;}else{return 0;}";
        passThroughTest.Program.evalStatement(a);
    }
    public static void evalStatement(String statement)
    {

        //Evaluation of Statement

     }

This isn't perfect but in this case the end result would be a 1. This seems 'stupid' from this point of view, but its for a more complex engine which needs to draw on similar syntax to evaluate.

Am I at a point where I need to write a parser of some sort and evaluate the statements...?

Thanks for your help!

How complex are your statements going to be? http://stackoverflow.com/questions/826398/is-it-possible-to-dynamically-compile-and-execute-c-sharp-code-fragments is a text book example of using the CodeDom — dash, Oct 19 '12 at 23:35
Thank you for that link. Im going to dig into it a little more. It should not be too complex; though it could get to a point where its nesting ifs or using switch statements. — Alex Kremer, Oct 19 '12 at 23:56
This is best and awesome method CLICK [Here](http://stackoverflow.com/questions/1437964/best-and-shortest-way-to-evaluate-mathematical-expressions/1438829#1438829) — Sarbanjeet, Mar 26 '14 at 12:14

score 3 · Answer 1 · answered Oct 19 '12 at 23:35

3

What I think you are looking for is the CSharpCodeProvider : http://msdn.microsoft.com/en-us/library/microsoft.csharp.csharpcodeprovider.aspx

This allows you to compile or evaluate C# code from a source and run it. It might not be as easy as evaluating a single "if" case, as when you compile C#, you are expected to have the whole syntax coming with it.

answered Oct 19 '12 at 23:35

LightStriker

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Thank you for the response. Im going to dig into that one and see how it compares to some of the other answers. – Alex Kremer Oct 20 '12 at 00:06

score 3 · Accepted Answer · edited Jan 17 '18 at 04:41

You can use javascript.net

Sample code from their website:

// Initialize a context
using (JavascriptContext context = new JavascriptContext()) {

    // Setting external parameters for the context
    context.SetParameter("console", new SystemConsole());
    context.SetParameter("message", "Hello World !");
    context.SetParameter("number", 1);

    // Script
    string script = @"
        var i;
        for (i = 0; i < 5; i++)
            console.Print(message + ' (' + i + ')');
        number += i;
    ";

    // Running the script
    context.Run(script);

    // Getting a parameter
    Console.WriteLine("number: " + context.GetParameter("number"));
}

Or use C# expression tree, see Building Expression Evaluator with Expression Trees

This method seems like it would use less overhead in the long run... Im going to try it out and see how it works. Thanks! — Alex Kremer, Oct 20 '12 at 00:04

score 0 · Answer 3 · answered Oct 19 '14 at 22:37

You can also do something like this:

var expression="(\"Alex\" == \"Alex\") ? 1:0"; 
var res = FlexRule.DynamicEvaluation.ExpressionEval.Default.Compute(null, expression);

For more details information of expression please have a look at http://wiki.flexrule.com/index.php?title=Expression

Dynamic C# Formula Evaluation

3 Answers3