/**********************************************************************************************

* This fiddle is a demo of the library : CodingSeb.ExpressionEvaluator

* See : https://github.com/codingseb/ExpressionEvaluator

* For Others examples : https://dotnetfiddle.net/Packages/41132/CodingSeb_ExpressionEvaluator

**********************************************************************************************/

​

using System;

using System.Collections.Generic;

using CodingSeb.ExpressionEvaluator;

public class Program

{

    public static void Main()

    {

        ExpressionEvaluator evaluator = new ExpressionEvaluator();

        // always evaluated before other var and func evaluations 

        evaluator.PreEvaluateVariable += Evaluator_PreEvaluateVariable;

        evaluator.PreEvaluateFunction += Evaluator_PreEvaluateFunction;

​

        // evaluated if no existing var or func exists

        evaluator.EvaluateVariable += Evaluator_EvaluateVariable;

        evaluator.EvaluateFunction += Evaluator_EvaluateFunction;

        List<string> expressions = new List<string>()

        {

            "myvar1 + 2",

            "Pi",

            "Test(5)",

            "Abs(-3)",

            "myVar2 + 2",

            "SayHello(\"Bob\")",

            "3.MultipliedBy2",

            "3.Add(2)",

            "GenericNamespace<List<string>>()",

            "GenericAssembly<string>"

        };

        expressions.ForEach(expression => 

        {

            try

            {

                Console.WriteLine(expression);

                Console.WriteLine(evaluator.Evaluate(expression));

            }

            catch (Exception exception)

            {

                Console.WriteLine("throw an exception : " + exception.Message);

            }

            finally

            {

                Console.WriteLine(string.Empty);

            }

        });

    }

    private static void Evaluator_PreEvaluateVariable(object sender, VariablePreEvaluationEventArg e)

    {

        if (e.Name.Equals("myvar1"))

        {

            e.Value = 5;

        }

        else if(e.Name.StartsWith("P"))

        {

            e.CancelEvaluation = true;

        }

    }

​

    private static void Evaluator_PreEvaluateFunction(object sender, FunctionPreEvaluationEventArg e)

    {

        if(e.Name.Equals("Test") && e.Args.Count == 1)

        {

            e.Value = "It is a test for " + e.EvaluateArg(0);

        }

        else if(e.Name.StartsWith("A"))

        {

            e.CancelEvaluation = true;

        }

    }

​

    private static void Evaluator_EvaluateVariable(object sender, VariableEvaluationEventArg e)

    {

        if(e.Name.ToLower().Equals("myvar2"))

        {

            e.Value = 8;

        }

        else if(e.Name.Equals("MultipliedBy2") && e.This is int)

        {

            e.Value = (int)e.This * 2;

        }

        else if (e.Name.Equals("GenericAssembly") && e.HasGenericTypes)

        {

            // e.EvaluateGenericTypes() return a Type[]

            e.Value = e.EvaluateGenericTypes()[0].Assembly.GetName().Name;

        }

    }

​

    private static void Evaluator_EvaluateFunction(object sender, FunctionEvaluationEventArg e)

    {

        if(e.Name.ToLower().Equals("sayhello") && e.Args.Count == 1)

        {

            e.Value = "Hello " + e.EvaluateArg(0);

        }

        else if(e.Name.Equals("Add") && e.This is int)

        {

            e.Value = (int)e.This + (int)e.EvaluateArg(0);

        }

        else if(e.Name.Equals("GenericNamespace") && e.HasGenericTypes)

        {

            // e.EvaluateGenericTypes() return a Type[]

            e.Value = e.EvaluateGenericTypes()[0].Namespace;

        }

    }

}