Just add the resource header file.
#include "Resource.h"
Send message in MFC thread
1. Write the meaning first and accept it
#define WM_SET_FOCUS WM_USER+100
BEGIN_MESSAGE_MAP(CWriteSnDlg, CDialogEx)
//
ON_MESSAGE(WM_SET_FOCUS, OnSetFocus)
END_MESSAGE_MAP()
afx_msg LRESULT OnSetFocus(WPARAM wP, LPARAM lp);
LRESULT CWriteSnDlg::OnSetFocus(WPARAM wP, LPARAM lp)
{
UNREFERENCED_PARAMETER(wP);
UNREFERENCED_PARAMETER(lp);
GetDlgItem(IDC_EDIT1)->SetFocus();
return 0;
}
2. Send message
UINT WriteSNProc(LPVOID lParam){
CWriteSnDlg *pWnd = (CWriteSnDlg *)lParam;
PostMessage(*pWnd,WM_SET_FOCUS, NULL,NULL);
//SendMessage(*pWnd,WM_SET_FOCUS, NULL,NULL);
}
PostMessage(this,WM_SET_FOCUS, NULL,NULL);