comment *
ml /c /coff dlltest.asm
link /dll dlltest.obj
*

.386
.model flat

.code

DllEntry proc stdcall hinstDLL:DWORD, fdwReason:DWORD, lpReserved:DWORD
    mov eax, 1
    ret
DllEntry endp

myadd proc stdcall export a:DWORD, b:DWORD
    mov eax, a
    add eax, b
    ret
myadd endp

mysub proc stdcall export a:DWORD, b:DWORD
    mov eax, a
    sub eax, b
    ret
mysub endp

end DllEntry

@echo off
path %path%;C:\masm32\bin
path %path%;C:\Windows\Microsoft.NET\Framework\v4.0.30319
cmd

// csc /platform:x86 dlltest.cs

using System;
using System.Runtime.InteropServices;

class Program {
    [DllImport("dlltest.dll")]
    static extern int myadd(int a, int b);
    [DllImport("dlltest.dll")]
    static extern int mysub(int a, int b);

    static void Main() {
        Console.WriteLine("add = {0}", myadd(1, 2));
        Console.WriteLine("sub = {0}", mysub(1, 2));
    }
}

comment *
ml /c /coff dllclt.asm
link /subsystem:console dllclt
*

includelib kernel32.lib
includelib user32.lib
includelib dlltest.lib

.386
.model flat, stdcall
option casemap:none

include windows.inc
include kernel32.inc
include user32.inc

mysub proto stdcall :DWORD, :DWORD

.const
fmt db  'sub = %d', 0dh, 0ah, 0

.data?
hStdOut dd  ?
written dd  ?
len dd  ?
buf db  1024 dup (?)

.code
start:
    invoke  GetStdHandle, STD_OUTPUT_HANDLE
    mov hStdOut, eax
    invoke  mysub, 1, 2
    invoke  wsprintf, addr buf, addr fmt, eax
    mov len, eax
    cld
    invoke  WriteConsole, hStdOut, addr buf, len, addr written, NULL
    invoke  ExitProcess, 0

end start

@echo off
path %path%;C:\masm32\bin
set INCLUDE=C:\masm32\include
set LIB=C:\masm32\lib
cmd