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JIT Compiler error - Invalid Program Exception using Reflection.Emit

Can someone explain to me why the following works for the first test but throws an InvalidProgramException for the second test? I'm stumped.

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

namespace DMTest { class Program { static void Main(string[] args) { Test.NewResultWithParam(); Console.WriteLine("Press any key to continue"); Console.ReadLine(); Test.NewResult(); Console.WriteLine("Press any key to exit"); Console.ReadLine(); } }

public static class Test { public static void NewResult() { var f = typeof(Result).New<Result>(); var result = f.Invoke(); } public static void NewResultWithParam() { var f = typeof(Result).New<Param, Result>(); var result = f.Invoke(new Param("Parameter Executed")); result.Build(); } } publi开发者_JAVA百科c static class DynamicFunctions { public static Func<R> New<R>(this Type type) { if (!typeof(R).IsAssignableFrom(type)) { throw new ArgumentException(); } var dm = BuildNewMethod(type, Type.EmptyTypes); return (Func<R>)dm.CreateDelegate(typeof(Func<R>)); } public static Func<T, R> New<T, R>(this Type type) { if (!typeof(R).IsAssignableFrom(type)) { throw new ArgumentException(); } var dm = BuildNewMethod(type, new Type[] { typeof(T) }); return (Func<T, R>)dm.CreateDelegate(typeof(Func<T, R>)); } private static DynamicMethod BuildNewMethod(Type newObjType, Type[] parameterTypes) { var dm = new DynamicMethod("New_" + newObjType.FullName, newObjType, parameterTypes, newObjType); var info = newObjType.GetConstructor(BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public, null, parameterTypes, new ParameterModifier[0]); ILGenerator il = dm.GetILGenerator(); il.Emit(OpCodes.Ldarg_0); il.Emit(OpCodes.Newobj, info); il.Emit(OpCodes.Ret); return dm; } } public class Result { private Param _param; private Result() { Console.WriteLine("Parameterless constructor called"); } private Result(Param param) { Console.WriteLine("Parametered constructor called"); _param = param; } public void Build() { _param.Execute(); } } public class Param { private string _s; public Param(string s) { _s = s; } public void Execute() { Console.WriteLine(_s); } }

}


il.Emit(OpCodes.Ldarg_0); // <-- problem here

Since your dynamic method doesn't have parameters in the New<T> version, you can't use Ldarg_0. Also, Newobj will expect zero arguments, so your stack is unbalanced.

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