Marshal --> ( Marshal.GetFunctionPointerForDelegate GetDelegateForFunctionPointer)

GetDelegateForFunctionPointer.cs

 public static partial class Util
    {
        const string kDelegateInvokeMethodName = "Invoke";
        // http://www.codeproject.com/Tips/441743/A-look-at-marshalling-delegates-in-NET
        public static T GetDelegateForFunctionPointer<T>(IntPtr ptr, System.Runtime.InteropServices.CallingConvention call_conv)
            where T : class
        {
            Contract.Requires<ArgumentException>(typeof(T).IsSubclassOf(typeof(Delegate)));
            Contract.Requires<ArgumentNullException>(ptr != IntPtr.Zero);
            Contract.Requires<ArgumentException>(call_conv != System.Runtime.InteropServices.CallingConvention.ThisCall,
                "TODO: ThisCall's require a different implementation");

            Contract.Ensures(Contract.Result<T>() != null);

            var type = typeof(T);
            var method = type.GetMethod(kDelegateInvokeMethodName);
            var ret_type = method.ReturnType;
            var param_types = (from param in method.GetParameters()
                               select param.ParameterType)
                              .ToArray();

            var invoke = new System.Reflection.Emit.DynamicMethod(kDelegateInvokeMethodName, ret_type, param_types,
                typeof(Delegate));
            var il = invoke.GetILGenerator();

            // Generate IL for loading all the args by index
            // TODO: IL has Ldarg_0 to Ldarg_3...do these provide any tangible perf benefits?
            for (int x = 0; x < param_types.Length; x++)
                il.Emit(System.Reflection.Emit.OpCodes.Ldarg, x);

            // Generate the IL for Calli's entry pointer (pushed to the stack)
            if (Environment.Is64BitProcess)
                il.Emit(System.Reflection.Emit.OpCodes.Ldc_I8, ptr.ToInt64());
            else
                il.Emit(System.Reflection.Emit.OpCodes.Ldc_I4, ptr.ToInt32());

            il.EmitCalli(System.Reflection.Emit.OpCodes.Calli, call_conv, ret_type, param_types);
            il.Emit(System.Reflection.Emit.OpCodes.Ret);

            return invoke.CreateDelegate(type) as T;
        }
    };

GetFunctionPointerForDelegate.cs

  public static IntPtr GetFunctionPointerForDelegate<T>(T delegateCallback, out object binder)
            where T : class
        {
            var del = delegateCallback as Delegate;
            IntPtr result;

            try
            {
                result = Marshal.GetFunctionPointerForDelegate(del);
                binder = del;
            }
            catch (ArgumentException) // generic type delegate
            {
                var delegateType = typeof (T);
                var method = delegateType.GetMethod("Invoke");
                var returnType = method.ReturnType;
                var paramTypes =
                    method
                        .GetParameters()
                        .Select((x) => x.ParameterType)
                        .ToArray();

                // builder a friendly name for our assembly, module, and proxy type
                var nameBuilder = new StringBuilder();
                nameBuilder.Append(delegateType.Name);
                foreach (var pType in paramTypes)
                {
                    nameBuilder
                        .Append("`")
                        .Append(pType.Name);
                }
                var name = nameBuilder.ToString();

                // check if we've previously proxied this type before
                var proxyAssemblyExist =
                    AppDomain
                        .CurrentDomain
                        .GetAssemblies()
                        .FirstOrDefault((x) => x.GetName().Name == name);

                Type proxyType;
                if (proxyAssemblyExist == null)
                {
                    /// create a proxy assembly
                    var proxyAssembly = AppDomain.CurrentDomain.DefineDynamicAssembly(
                        new AssemblyName(name),
                        AssemblyBuilderAccess.Run
                        );
                    var proxyModule = proxyAssembly.DefineDynamicModule(name);
                    // begin creating the proxy type
                    var proxyTypeBuilder = proxyModule.DefineType(name,
                        TypeAttributes.AutoClass |
                        TypeAttributes.AnsiClass |
                        TypeAttributes.Sealed |
                        TypeAttributes.Public,
                        typeof (MulticastDelegate)
                        );
                    // implement the basic methods of a delegate as the compiler does
                    var methodAttributes =
                        MethodAttributes.Public |
                        MethodAttributes.HideBySig |
                        MethodAttributes.NewSlot |
                        MethodAttributes.Virtual;
                    proxyTypeBuilder
                        .DefineConstructor(
                            MethodAttributes.FamANDAssem |
                            MethodAttributes.Family |
                            MethodAttributes.HideBySig |
                            MethodAttributes.RTSpecialName,
                            CallingConventions.Standard,
                            new Type[] {typeof (object), typeof (IntPtr)})
                        .SetImplementationFlags(
                            MethodImplAttributes.Runtime |
                            MethodImplAttributes.Managed
                        );
                    proxyTypeBuilder
                        .DefineMethod(
                            "BeginInvoke",
                            methodAttributes,
                            typeof (IAsyncResult),
                            paramTypes)
                        .SetImplementationFlags(
                            MethodImplAttributes.Runtime |
                            MethodImplAttributes.Managed);
                    proxyTypeBuilder
                        .DefineMethod(
                            "EndInvoke",
                            methodAttributes,
                            null,
                            new Type[] {typeof (IAsyncResult)})
                        .SetImplementationFlags(
                            MethodImplAttributes.Runtime |
                            MethodImplAttributes.Managed);
                    proxyTypeBuilder
                        .DefineMethod(
                            "Invoke",
                            methodAttributes,
                            returnType,
                            paramTypes)
                        .SetImplementationFlags(
                            MethodImplAttributes.Runtime |
                            MethodImplAttributes.Managed);
                    // create & wrap an instance of the proxy type
                    proxyType = proxyTypeBuilder.CreateType();
                }
                else
                {
                    // pull the type from an existing proxy assembly
                    proxyType = proxyAssemblyExist.GetType(name);
                }
                // marshal and bind the proxy so the pointer doesn't become invalid
                var repProxy = Delegate.CreateDelegate(proxyType, del.Target, del.Method);
                result = Marshal.GetFunctionPointerForDelegate(repProxy);
                binder = Tuple.Create(del, repProxy);
            }
            return result;
        }

Test.cs

using System;
using System.Linq;
using System.Reflection;
using System.Reflection.Emit;
using System.Runtime.InteropServices;
using System.Text;
using Xunit;

namespace Class1sharp
{
    public class Program
    {
    
        [System.Flags]
        private enum LoadLibraryFlags : uint
        {
            DONT_RESOLVE_DLL_REFERENCES = 0x00000001,
            LOAD_IGNORE_CODE_AUTHZ_LEVEL = 0x00000010,
            LOAD_LIBRARY_AS_DATAFILE = 0x00000002,
            LOAD_LIBRARY_AS_DATAFILE_EXCLUSIVE = 0x00000040,
            LOAD_LIBRARY_AS_IMAGE_RESOURCE = 0x00000020,
            LOAD_WITH_ALTERED_SEARCH_PATH = 0x00000008
        }

        [UnmanagedFunctionPointer(System.Runtime.InteropServices.CallingConvention.StdCall, SetLastError = true)]
        private delegate void ManagedTypeSignature(uint a, uint b);

        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        private static extern int MessageBox(IntPtr hWnd, String text, String caption, int options);

        [DllImport("kernel32.dll")]
        private static extern IntPtr LoadLibraryEx(string lpFileName, IntPtr hReservedNull, LoadLibraryFlags dwFlags);

        [DllImport("kernel32", SetLastError = true, CharSet = CharSet.Unicode)]
        private static extern IntPtr LoadLibrary(string lpFileName);

        [DllImport("kernel32", CharSet = CharSet.Ansi, ExactSpelling = true, SetLastError = true)]
        internal static extern IntPtr GetProcAddress(IntPtr hModule, string procName);

        [DllImport("kernel32.dll", SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        static extern bool FreeLibrary(IntPtr hModule);



        internal delegate int DllRegisterServerInvoker();


        public static IntPtr GetFunctionPointerForDelegate<T>(T delegateCallback, out object binder)
            where T : class
        {
            var del = delegateCallback as Delegate;
            IntPtr result;

            try
            {
                result = Marshal.GetFunctionPointerForDelegate(del);
                binder = del;
            }
            catch (ArgumentException) // generic type delegate
            {
                var delegateType = typeof (T);
                var method = delegateType.GetMethod("Invoke");
                var returnType = method.ReturnType;
                var paramTypes =
                    method
                        .GetParameters()
                        .Select((x) => x.ParameterType)
                        .ToArray();

                // builder a friendly name for our assembly, module, and proxy type
                var nameBuilder = new StringBuilder();
                nameBuilder.Append(delegateType.Name);
                foreach (var pType in paramTypes)
                {
                    nameBuilder
                        .Append("`")
                        .Append(pType.Name);
                }
                var name = nameBuilder.ToString();

                // check if we've previously proxied this type before
                var proxyAssemblyExist =
                    AppDomain
                        .CurrentDomain
                        .GetAssemblies()
                        .FirstOrDefault((x) => x.GetName().Name == name);

                Type proxyType;
                if (proxyAssemblyExist == null)
                {
                    /// create a proxy assembly
                    var proxyAssembly = AppDomain.CurrentDomain.DefineDynamicAssembly(
                        new AssemblyName(name),
                        AssemblyBuilderAccess.Run
                        );
                    var proxyModule = proxyAssembly.DefineDynamicModule(name);
                    // begin creating the proxy type
                    var proxyTypeBuilder = proxyModule.DefineType(name,
                        TypeAttributes.AutoClass |
                        TypeAttributes.AnsiClass |
                        TypeAttributes.Sealed |
                        TypeAttributes.Public,
                        typeof (MulticastDelegate)
                        );
                    // implement the basic methods of a delegate as the compiler does
                    var methodAttributes =
                        MethodAttributes.Public |
                        MethodAttributes.HideBySig |
                        MethodAttributes.NewSlot |
                        MethodAttributes.Virtual;
                    proxyTypeBuilder
                        .DefineConstructor(
                            MethodAttributes.FamANDAssem |
                            MethodAttributes.Family |
                            MethodAttributes.HideBySig |
                            MethodAttributes.RTSpecialName,
                            CallingConventions.Standard,
                            new Type[] {typeof (object), typeof (IntPtr)})
                        .SetImplementationFlags(
                            MethodImplAttributes.Runtime |
                            MethodImplAttributes.Managed
                        );
                    proxyTypeBuilder
                        .DefineMethod(
                            "BeginInvoke",
                            methodAttributes,
                            typeof (IAsyncResult),
                            paramTypes)
                        .SetImplementationFlags(
                            MethodImplAttributes.Runtime |
                            MethodImplAttributes.Managed);
                    proxyTypeBuilder
                        .DefineMethod(
                            "EndInvoke",
                            methodAttributes,
                            null,
                            new Type[] {typeof (IAsyncResult)})
                        .SetImplementationFlags(
                            MethodImplAttributes.Runtime |
                            MethodImplAttributes.Managed);
                    proxyTypeBuilder
                        .DefineMethod(
                            "Invoke",
                            methodAttributes,
                            returnType,
                            paramTypes)
                        .SetImplementationFlags(
                            MethodImplAttributes.Runtime |
                            MethodImplAttributes.Managed);
                    // create & wrap an instance of the proxy type
                    proxyType = proxyTypeBuilder.CreateType();
                }
                else
                {
                    // pull the type from an existing proxy assembly
                    proxyType = proxyAssemblyExist.GetType(name);
                }
                // marshal and bind the proxy so the pointer doesn't become invalid
                var repProxy = Delegate.CreateDelegate(proxyType, del.Target, del.Method);
                result = Marshal.GetFunctionPointerForDelegate(repProxy);
                binder = Tuple.Create(del, repProxy);
            }
            return result;
        }


        public delegate int MessageBoxDelegate(IntPtr hWnd, string lpText, string lpCaption, uint uType);

        public delegate int Posy(int a, int b);

        [Fact]
        public static void Main()
        {


            // let's get a managed method and convert it to an int:
            var managedMethod = new ManagedTypeSignature(MyManagedMethod);
            var untypedManagedMethod = (Delegate) managedMethod;
            IntPtr nativeThunk = Marshal.GetFunctionPointerForDelegate(untypedManagedMethod);


            // nativeThunk can now be called by C++ using the following typedef:
            // void (__stdcall *NativeTypeSignature) ( uint32_t a, uint32_t b );

            // now let's turn it back into a function:
            Delegate untypedNativeMethod = Marshal.GetDelegateForFunctionPointer(nativeThunk, typeof (ManagedTypeSignature));
            var managedMethod2 = (ManagedTypeSignature) untypedNativeMethod;

            // let's call it, just to be sure:
            managedMethod2(37, 4);

            Posy m = (i, i1) => i + i1;

            var tx=  Marshal.GetFunctionPointerForDelegate(m);

            //var ptr = GetProcAddress(LoadLibraryA("user32.dll"), "MessageBoxA");
            //var MessageBoxA =
            //   GetDelegateForFunctionPointer<Func<IntPtr, string, string,
            //   int, int>>(ptr, CallingConvention.StdCall);
            //MessageBoxA(IntPtr.Zero, "Hello world", "Test", 0);
        }

        private static void MyManagedMethod(uint a, uint b)
        {
            Console.Write("{0} + {1} = {2}", a, b, a + b);
        }

        [Fact]
        public void Testd()
        {
            //var module = LoadLibrary("user32.dll");
            //// Can't use MessageBoxW, seems to implicitly marshal to UTF8? Could have sworn .NET strings were internally UTF16
            //// Then again, my system is setup for en-us...
            //var proc_ptr = GetProcAddress(module, "MessageBoxA");
            //const System.Runtime.InteropServices.CallingConvention call_conv =
            //    System.Runtime.InteropServices.CallingConvention.Winapi;

            //var msg_box = Util.GetDelegateForFunctionPointer<MessageBoxDelegate>(proc_ptr, call_conv);
            //msg_box(IntPtr.Zero, "Hello World", "Test1", 0);

            //var msg_box_gen = Util.GetDelegateForFunctionPointer<MessageBoxDelegateGeneric>(proc_ptr, call_conv);
            //msg_box_gen(IntPtr.Zero, "Goodbye World", "Test2", 0);

            //Func<int, int> c = (x) =>x;

            //IntPtr functionPointerForDelegate = Marshal.GetFunctionPointerForDelegate(c);

            object ttys;

            IntPtr pointerForDelegate = GetFunctionPointerForDelegate<Func<int, int>>(i => 1, out ttys);

            Console.Write(pointerForDelegate);
            Marshal.GetDelegateForFunctionPointer()

            //  FreeLibrary(module);
        }


    
    }
}