How to pass a CString from one application to another application using WPARAM/LPARAM in sendmessage fn.

Question

I have two different application A & B. I am trying to send a message from A to B. In application A , I get the window handle of application B and call postmessage fn to post a message to application B. While posting the message I am trying to send a
cstring in wparam parameter so that it can be accessed in the message handler.
Code in Application A:
void CTestApplnDlg::OnBnClickedOk()
 CString csProcessName = _T("FSAPP.exe");
 CFSProcess objProcess;
 HWND hFSWnd = NULL;
 if(objProcess.GetProcessHandle(csProcessName, hFSWnd))
  CString * csMessage = new CString(_T("This is message from A application."));
  ::PostMessage(hFSWnd, WM_THIRD_PARTY_NOTIFICATION, (WPARAM)csMessage
, NULL);
In the other application in the event event handler I try to do the following :
LRESULT CMainFrame::OnProcessThirdPartyNotification(WPARAM wParam, LPARAM lParam)
 CString* csMessage = (CString*)wParam;
 if(csMessage )
  AfxMessageBox(*csMessage);
 return 0L;
In the message handler fn, the variable csMessage is pointing to a address but the value is a bad ptr. On accessing the variable like *csMessage it crashes. I have created the variable in heap when the message is posted. So I hope the variable will be in memory.
Pls help.

Answer 1

The ultimate problem is that when you place a CString in a wparam like that you are putting an address.  That address only has meaning in the first program.  Your second program cannot access the first programs memory (this is good, otherwise misbehaving
programs could take down all applications in Windows).  But it does make transferring data between programs more complicated. 
Some messages like WM_COPYDATA will copy a data buffer from one process to another and are appropriate for what you are trying to do, but a custom message like
WM_THIRD_PARTY_NOTIFICATION is not one of them.
By the way your example has a memory leak as well since you would have no way to ever clean up the string you allocate in OnBnClickedOk