Crash after using cprintdialog

It is not a crash but an assertion is thrown. Assertions are only thrown in debug builds. They are mainly used to inform you during development that something weird has happened (read: the developer has made a serious mistake).

When mentioning a line number within an MFC source file like wincore.cpp, you should also mention the used VS version or better open that file (it is located at VC\atlmfc\src\mfc) and add the function name and the line content.

With my wincore.cpp version the lines 412 to 414 are

CWnd* pWnd = CWnd::FromHandlePermanent(hWnd);
ASSERT(pWnd != NULL);					
ASSERT(pWnd==NULL || pWnd->m_hWnd == hWnd);

with the AfxWndProc() function.

Run the program from the debugger and check the call stack when the assertion occurs to know for which window the function is called.

Read also about the CPrintDialog Class[^] and check if your code applies. Because you are creating the print dialog on the stack, it is deleted when going out of scope. Then an assertion for that window would occur earlier and not when closing the application. So the real reason for the assertion might be somewhere else in your application.

For better help you should post the complete function that uses the print dialog. Something like

void SomeClass::SomeFunc()
{
    BOOL bPrintSetupOnly = FALSE;
    CPrintDialog dlg(bPrintSetupOnly);
    if (dlg.DoModal() == IDOK)
    {
        // do something here

        // If dlg.m_pd.hDC has not been assigned to a member variable
        if (!bPrintSetupOnly) // or GetDefaults, or GetPrinterDC has been called
            DeleteDC(dlg.m_pd.hDC);
        // Otherwise do it when not used anymore 
        //  (at least when this SomeClass instance destroyed).
        // But that requires tracking the state (clear member variable after deleting)
        //  and deleting it also on top of this function when not NULL
    }
}