Juz a stupid Q, and take a look the code shown below:

Code:
    Dim hdc As Long
    Dim hPen As Long
    Dim hOldPen As Long
    Dim pt As POINTAPI
    
    hdc = GetDC(Form1.hwnd)
    hPen = CreatePen(PS_SOLID, RGB(0, 255, 255))
    hOldPen = SelectObject(hdc, hPen)
    Polyline hdc, pt(0), 5
    SelectObject hdc, hOldPen
    DeleteObject hPen
    ReleaseDC Form1.hwnd, hdc
Why there is a need to restore the old pen object into the device Context (DC)? What will happen if I does not restore it?