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Understanding The COM Single-Threaded Apartment Part 1

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6 Jan 2005CPOL49 min read 839.3K   4.9K   441  
Learn the fundamental principles of the COM Single-Threaded Apartment Model by code examples.
#define _WIN32_WINNT 0x0400
#include <windows.h>
#include <stdio.h>

#import "..\..\..\..\SimpleCOMObject2\Debug\SimpleCOMObject2.dll"
using namespace SIMPLECOMOBJECT2Lib;





// Simple function that displays the current thread ID.
void DisplayCurrentThreadId()
{
  TCHAR szMessage[256];

  sprintf (szMessage, "Thread ID : 0x%X", GetCurrentThreadId());

  ::MessageBox(NULL, szMessage, "TestMethod1()", MB_OK);
}





DWORD WINAPI ThreadFunc(LPVOID lpvParameter)
{
  ::CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);

  DisplayCurrentThreadId();

  if (1)
  {
    ISimpleCOMObject2Ptr spISimpleCOMObject2A;
	ISimpleCOMObject2Ptr spISimpleCOMObject2B;

    spISimpleCOMObject2A.CreateInstance(__uuidof(SimpleCOMObject2));
	spISimpleCOMObject2B.CreateInstance(__uuidof(SimpleCOMObject2));

	spISimpleCOMObject2A -> TestMethod1();
	spISimpleCOMObject2B -> TestMethod1();
  }

  ::CoUninitialize();

  return 0;
}





int main()
{
  HANDLE hThread = NULL;
  DWORD  dwThreadId = 0;

  ::CoInitializeEx(NULL, COINIT_APARTMENTTHREADED);

  DisplayCurrentThreadId();

  if (1)
  {
    ISimpleCOMObject2Ptr spISimpleCOMObject2;

    spISimpleCOMObject2.CreateInstance(__uuidof(SimpleCOMObject2));

    spISimpleCOMObject2 -> TestMethod1();

    hThread = CreateThread
    (
      (LPSECURITY_ATTRIBUTES)NULL, // SD
      (SIZE_T)0,                       // initial stack size
      (LPTHREAD_START_ROUTINE)ThreadFunc,    // thread function
      (LPVOID)NULL,                       // thread argument
      (DWORD)0,                    // creation option
      (LPDWORD)&dwThreadId                        // thread identifier
    );

    WaitForSingleObject(hThread, INFINITE);

	spISimpleCOMObject2 -> TestMethod1();
  }

  ::CoUninitialize();

  return 0;
}





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License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


Written By
Systems Engineer NEC
Singapore Singapore
Lim Bio Liong is a Specialist at a leading Software House in Singapore.

Bio has been in software development for over 10 years. He specialises in C/C++ programming and Windows software development.

Bio has also done device-driver development and enjoys low-level programming. Bio has recently picked up C# programming and has been researching in this area.

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