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.

IE

    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!

Answer 1

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.

Answer 2

• 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

Answer 3

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