// C# Eval Expression

// Doc: https://eval-expression.net/options

​

// @nuget: Z.Expressions.Eval

​

/*

## DisableConstantFolding

​

The DisableConstantFolding option lets you to get or set if constant folding should be disabled. Constant folding is the logic to replace an equation with 2 constants like `2+3` directly into the constant `5`. This avoids running the addition every time the compiled method is executed.

​

In this example, we will compile a basic addition expression with 2 constants. By exploring the last compiled expression, we will show the difference when a constant was used with constant folding versus when the addition was used with constant folding turned off.

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See more: https://eval-expression.net/options

*/

​

using System;

using System.Collections.Generic;

using System.Linq.Expressions;

using System.Reflection;

using Z.Expressions;

​

public class Program

{

    public static void Main()

    {

        // Global Context: EvalManager.DefaultContext.DisableConstantFolding = true;

        var expression = "2+3";

        // Example 1 - with constant folding enabled

        {

            var context = new EvalContext();    

            var compiled = context.Compile<Func<int>>(expression);

            var lastExpression = context.LastCompiledExpression;

            Console.WriteLine($"Constant Folding Enabled; NodeType: {lastExpression.NodeType}; Value {((ConstantExpression)lastExpression).Value}");

        }   

        // Example 1 - with constant folding disabled

        {

            var context = new EvalContext();

            context.DisableConstantFolding = true;

            var compiled = context.Compile<Func<int>>(expression);

            var lastExpression = context.LastCompiledExpression;

            Console.WriteLine($"Constant Folding Disabled; NodeType: {lastExpression.NodeType}; LeftValue: {((ConstantExpression)((BinaryExpression)lastExpression).Left).Value}; RightValue: {((ConstantExpression)((BinaryExpression)lastExpression).Right).Value};");

        }

    }

}