// HelloWorld... the HARD way!
// Copyright (C) Raoul Millais - Just in case you thougth you might steal this higly valuable code ;)

using System;
using System.Collections.Generic;
using System.Text;

using System.Reflection.Emit;
using System.Reflection;

namespace DynamicAssemblyDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            // Define the dynamic assembly
            AssemblyName name = new AssemblyName("MyTempAssembly");
            name.Version = new Version("1.0.0.0");
            AppDomain currentAppDomain = AppDomain.CurrentDomain;
            AssemblyBuilder tempAssembly = 
                currentAppDomain.DefineDynamicAssembly(name, AssemblyBuilderAccess.Run);
            
            // Define the module
            ModuleBuilder tempModule = tempAssembly.DefineDynamicModule("MyTempAssembly.dll");
            TypeBuilder tempType = tempModule.DefineType("TempType", TypeAttributes.Public);

            // Define the SayHello static method
            MethodAttributes publicStatic = MethodAttributes.Public | MethodAttributes.Static;
            MethodBuilder sayHelloMethod = tempType.DefineMethod("SayHello", 
                publicStatic, typeof(void), Type.EmptyTypes);
            
            // Get method info for Console.WriteLine(String) and Console.Read()
            string path = @"C:\Windows\Microsoft.NET\Framework\v2.0.50727\mscorlib.dll";
            Assembly mscorlib = Assembly.LoadFile(path);
            Type consoleType = mscorlib.GetType("System.Console");
            MethodInfo writeLineMethod = consoleType.GetMethod("WriteLine", new Type[] { typeof(string) });
            MethodInfo readMethod = consoleType.GetMethod("Read", Type.EmptyTypes);
            
            // Create the method body
            ILGenerator sayHelloCodeGen = sayHelloMethod.GetILGenerator();
            
            sayHelloCodeGen.Emit(OpCodes.Ldstr, "Hello World!");
            sayHelloCodeGen.EmitCall(OpCodes.Call, writeLineMethod, null);
            sayHelloCodeGen.Emit(OpCodes.Nop);
            sayHelloCodeGen.EmitCall(OpCodes.Call, readMethod, null);
            sayHelloCodeGen.Emit(OpCodes.Pop);
            sayHelloCodeGen.Emit(OpCodes.Ret);

            // Call the dynamically created SayHello method
            Type newType = tempType.CreateType();
            MethodInfo sayHello = newType.GetMethod("SayHello", Type.EmptyTypes);
            sayHello.Invoke(null, new object[] { });
        }
    }
}