DllMain template to execute code in a .cpl file which is just a renamed DLL that exports a function CplApplet

Cplapplet.cpp

// dllmain.cpp : Defines the entry point for the DLL application.
#include "pch.h"
#include <Windows.h>

extern "C" __declspec(dllexport) LONG CplApplet()
{
	MessageBoxA(NULL, "Replace this message box with something more interesting...", "Control Panel", 0);
	return 1;
}

BOOL APIENTRY DllMain( HMODULE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
                     )
{
	switch (ul_reason_for_call)
	{
		case DLL_PROCESS_ATTACH:
		{
			CplApplet();
		}
		case DLL_THREAD_ATTACH:
		case DLL_THREAD_DETACH:
		case DLL_PROCESS_DETACH:
			break;
	}
	return TRUE;
}