class Program
    {
        static void Main(string[] args)
        {
            var values = new List<(double x, double y)>();

            Stopwatch compileTime = Stopwatch.StartNew();
            string ftext = "Math.Sin(x)+0.3*Math.Sin(15*x)";
            Func<double, double> f = CompileFunc(ftext);
            compileTime.Stop();

            Stopwatch computeTime = Stopwatch.StartNew();
            for (double x = 0; x < 1_000_000 * 2 * Math.PI; x += 0.1)
                values.Add((x, f(x)));
            computeTime.Stop();

            Console.WriteLine($"Compile time: {compileTime.ElapsedMilliseconds} ms, compute time: {computeTime.ElapsedMilliseconds} ms");
            Console.WriteLine("Computed values");
            foreach (var pair in values.Take(10))
                Console.WriteLine($"f({pair.x}) = {pair.y}");
            Console.ReadKey();
        }

        static string boilerplate = @"using System; public static class C {{ public static double F(double x) {{ return {0}; }} }}";

        static Func<double, double> CompileFunc(string source)
        {
            var classSource = string.Format(boilerplate, source);
            var asm = CompileToAssembly(classSource);
            var mi = asm.GetType("C").GetMethod("F");
            return (Func<double, double>)Delegate.CreateDelegate(typeof(Func<double, double>), mi);
        }

        static Assembly CompileToAssembly(string source)
        {
            CompilerResults cr = new CSharpCodeProvider().CompileAssemblyFromSource(
                new CompilerParameters()
                {
                    ReferencedAssemblies = { "System.dll" },
                    GenerateInMemory = true
                }, source);

            if (cr.Errors.HasErrors)
                throw new ArgumentException("Invalid source");

            return cr.CompiledAssembly;
        }
    }