Change DateTimePicker style on combobox selection fails

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C++

C

WinAPI

I am trying to change the style and date format of the DateTimePicker control on combobox' CBS_SELCHANGE notification.

When user selects one option, datetime picker should have spin control and show only year. If user selects other options, style should be reset to short date style and date format should show date as dd.mm.yyyy.

Here is the code I have so far:

case WM_COMMAND:
    switch(LOWORD(wParam))
    {
    case IDC_COMBO5:
        {
            if (HIWORD(wParam) == CBN_SELENDOK)  
            {
                int iSelected = ComboBox_GetCurSel((HWND)lParam);

                switch (i)
                {
                case 1:
                    {
                        DWORD_PTR dwStyle = 
                            GetWindowLongPtr(GetDlgItem(hDlg,
                               IDC_DATETIMEPICKER1), GWL_STYLE);
                        // remove short date style
                        dwStyle &= ~DTS_SHORTDATEFORMAT;
                        // add spin control
                        dwStyle |= DTS_UPDOWN;
                        SetWindowLongPtr(GetDlgItem(hDlg,
                            IDC_DATETIMEPICKER1), GWL_STYLE, dwStyle);

                        // set date format
                        DateTime_SetFormat(GetDlgItem(hDlg,
                            IDC_DATETIMEPICKER1), L"yyyy");
                    }
                    break;
                case -1:
                case 0:
                case 2:
                default:
                    {
                        DWORD_PTR dwStyle = 
                            GetWindowLongPtr(GetDlgItem(hDlg,
                                IDC_DATETIMEPICKER1), GWL_STYLE);
                        // remove spin control
                        dwStyle &= ~DTS_UPDOWN;
                        // restore short date format
                        dwStyle |= DTS_SHORTDATEFORMAT;
                        SetWindowLongPtr(GetDlgItem(hDlg,
                            IDC_DATETIMEPICKER1), GWL_STYLE, dwStyle);

                        // set date format
                        DateTime_SetFormat(GetDlgItem(hDlg,
                            IDC_DATETIMEPICKER1), L"dd'|'MM'|'yyyy");
                    }
                    break;
                }
            }
        }
        break; 
        // other cases...

Format gets changed properly, but spin control doesn't get added at all.

Running through debugger, I can see that it goes through my code and throws no exceptions -> I went to Debug->Exceptions and checked everything under Thrown.

I work on Windows 7 x86, using Visual Studio 2013.

I am targeting XP onward.

Can you help me to fix my code so I can achieve desired behavior?