using System;

using System.Data;

using System.Data.DataSetExtensions;

using System.Globalization;

using System.Diagnostics;

using System.Linq;

using System.Linq.Expressions;

using System.Collections;

using System.Collections.Generic;

using System.Threading;

using System.Threading.Tasks;

using System.Xml;

using System.Text;

using System.Xml.XPath;

using System.Xml.Linq;

using System.Drawing;

using System.Windows.Forms;

​

public class Program

{

    public static void Main()

    {

        var s2 = CreatePolynomialSequence (new[] { 1d, 2, 3 });     

        Console.WriteLine(s2(5));       

    }

     public static Func<int, double> CreatePolynomialSequence (params double[] coeff)

     {              

         // polynom builder

         // double argument

         var y = Expression.Variable(typeof(double), "y");  

         // func result

         var res = Expression.Variable(typeof(double), "res");       

         var expr = Expression.Assign(res, Expression.Constant(coeff[0]));

         // build polynom in format: ((a*x+b)*x+c)*x+d  <=>  a*x^3 + b*x^2 + c*x + d

         for (int i = 1; i < coeff.Length; i++)

         {

             expr = Expression.Add

                    (

                        Expression.Multiply(expr, y), 

                        Expression.Constant(coeff[i]) 

                    );

         }       

         // function body

         var x = Expression.Variable(typeof(int), "x"); 

         var block = Expression.Block

             (

                 new ParameterExpression[]{ y, res },  // local variables

                 new Expression[]

                 {

                     // cast int argument to double

                     Expression.Assign(y, Expression.Convert(x, typeof(double))),

                     //compute result

                     expr

                 }

            );

         return Expression.Lambda<Func<int, double>>(block, x).Compile();

     }

}