LoopCreatedWithIL

using System;
using System.Reflection.Emit;

namespace ConsoleApp2
{

    class Program
    {
        public static void Main()
        {
            int invokationOfHandMadeMethodResult = Calculate(10);
            Console.WriteLine(invokationOfHandMadeMethodResult);

            int invokationOfDynamicallyCreatedMethodResult = CreateCalculateMethod()(10);
            Console.WriteLine(invokationOfDynamicallyCreatedMethodResult);
        }

        public static Func<int, int> CreateCalculateMethod()
        {
            Type integerType = typeof(int);
            DynamicMethod dynamicMethod = new DynamicMethod("Calculate", integerType, new[] { integerType });

            //----------------------------------------------------------------

            ILGenerator il = dynamicMethod.GetILGenerator();

            Label loopStartLable = il.DefineLabel();
            Label methodReturnResultLable = il.DefineLabel();

            //-- Local variable [0] -> int result
            il.DeclareLocal(integerType);
            il.Emit(OpCodes.Ldc_I4_0);
            il.Emit(OpCodes.Stloc_0);

            //-- Local variable [1] -> int i
            il.DeclareLocal(integerType);
            il.Emit(OpCodes.Ldc_I4_0);
            il.Emit(OpCodes.Stloc_1);

            //-- Loop start check -> i < 10
            il.MarkLabel(loopStartLable);
            il.Emit(OpCodes.Ldloc_1);
            il.Emit(OpCodes.Ldc_I4, 10);
            il.Emit(OpCodes.Bge, methodReturnResultLable);

            //-- Loop body -> result += i * x (The next THREE steps)

            //-- 1. i * x
            il.Emit(OpCodes.Ldloc_1);
            il.Emit(OpCodes.Ldarg_0);
            il.Emit(OpCodes.Mul);

            //-- 2. result + (i * x)
            il.Emit(OpCodes.Ldloc_0);
            il.Emit(OpCodes.Add);

            //-- 3. result = result + (i * x)
            il.Emit(OpCodes.Stloc_0);

            //-- i++
            il.Emit(OpCodes.Ldloc_1);
            il.Emit(OpCodes.Ldc_I4_1);
            il.Emit(OpCodes.Add);
            il.Emit(OpCodes.Stloc_1);

            //-- Branch/Go to the beginning of the loop and repeat
            il.Emit(OpCodes.Br, loopStartLable);

            //-- End of method -> return result
            il.MarkLabel(methodReturnResultLable);
            il.Emit(OpCodes.Ldloc_0);
            il.Emit(OpCodes.Ret);

            //----------------------------------------------------------------

            Func<int, int> method = (Func<int, int>)dynamicMethod.CreateDelegate(typeof(Func<int, int>));

            return method;
        }

        public static int Calculate(int x)
        {
            int result = 0;
            for (int i = 0; i < 10; i++)
            {
                result += i * x;
            }

            return result;
        }
    }
}