Simple example of dynamically compiled code that can access data in the program that compiles the assembly

dynamic_compilation.cs

using System;
using System.Diagnostics;
using System.Linq;

namespace csharpdynamiccompilationtest
{
    public class RegularClass
    {
        public static int Get(int[] i) { return i.Sum() + Program.rng.Next(1, 5); }
    }

    public class Program
    {
        public static Random rng = new Random();

        public static int k = 5;

        static void Main(string[] args)
        {
            var refs = AppDomain.CurrentDomain.GetAssemblies();
            var refFiles = refs.Where(a => !a.IsDynamic).Select(a => a.Location).ToArray();
            var cSharp = new Microsoft.CSharp.CSharpCodeProvider();
            var compileParams = new System.CodeDom.Compiler.CompilerParameters(refFiles)
            {
                GenerateInMemory = true,
                GenerateExecutable = false
            };

            string code = "using System; using System.Linq; namespace csharpdynamiccompilationtest { public class DynamicClass { public static int Get(int[] i ) { return i.Sum() + Program.rng.Next(1, 5); }} } ";
            string className = "csharpdynamiccompilationtest.DynamicClass";

            var compilerResult = cSharp.CompileAssemblyFromSource(compileParams, code);
            if (compilerResult.Errors.HasErrors)
            {
                foreach (var error in compilerResult.Errors)
                {
                    Console.WriteLine(error);
                }
                Console.ReadLine();
                return;
            }
            
            var asm = compilerResult.CompiledAssembly;

            var tempType = asm.GetType(className);
            var method = tempType.GetMethod("Get");
            Stopwatch stopWatch = new Stopwatch();
            long resolution = 1000000000 / Stopwatch.Frequency;
            Console.WriteLine("The minimum measurable time on this system is: {0} nanoseconds", resolution);
            var id = 0;
            int[] ints = new int[10000];
            for(int i = 0; i < 10000; i++)
            {
                ints[i] = rng.Next(1, 100);
            }

            stopWatch.Start();
            id += (int)method.Invoke(null, new object[1] { ints });
            stopWatch.Stop();
            Console.WriteLine("value returned: {0}", id);
            long nanoseconds = resolution * stopWatch.ElapsedTicks;
            Console.WriteLine("first invocation: {0} nanoseconds", nanoseconds);

            stopWatch = new Stopwatch();
            id = 0;
            stopWatch.Start();
            id += (int)method.Invoke(null, new object[1] { ints });
            stopWatch.Stop();
            Console.WriteLine("value returned: {0}", id);
            nanoseconds = resolution * stopWatch.ElapsedTicks;
            Console.WriteLine("second invocation: {0} nanoseconds", nanoseconds);

            id = 0;
            stopWatch = new Stopwatch();
            stopWatch.Start();
            id += RegularClass.Get(ints);
            stopWatch.Stop();
            Console.WriteLine("value returned from RegularClass: {0}", id);
            nanoseconds = resolution * stopWatch.ElapsedTicks;
            Console.WriteLine("first RegularClass invocation: {0} nanoseconds", nanoseconds);

            id = 0;
            stopWatch = new Stopwatch();
            stopWatch.Start();
            id += RegularClass.Get(ints);
            stopWatch.Stop();
            Console.WriteLine("value returned from RegularClass: {0}", id);
            nanoseconds = resolution * stopWatch.ElapsedTicks;
            Console.WriteLine("second RegularClass invocation: {0} nanoseconds", nanoseconds);
            Console.ReadLine();
        }
    }
}