C# Constants:

    static readonly int GWL_WNDPROC     =(-4);
    static readonly int GWL_HINSTANCE       =(-6);
    static readonly int GWL_HWNDPARENT      =(-8);
    static readonly int GWL_STYLE       =(-16);
    static readonly int GWL_EXSTYLE     =(-20);
    static readonly int GWL_USERDATA    =(-21);
    static readonly int GWL_ID          =(-12);

VB Constants:

    Public Const GWL_WNDPROC = (-4)
    Public Const GWL_HINSTANCE = (-6)
    Public Const GWL_HWNDPARENT = (-8)
    Public Const GWL_STYLE = (-16)
    Public Const GWL_EXSTYLE = (-20)
    Public Const GWL_USERDATA = (-21)
    Public Const GWL_ID = (-12)

C# Enum:

    public enum GetWindowLongConst
    {
        GWL_WNDPROC = (-4),
        GWL_HINSTANCE = (-6),
        GWL_HWNDPARENT = (-8),
        GWL_STYLE = (-16),
        GWL_EXSTYLE = (-20),
        GWL_USERDATA = (-21),
        GWL_ID = (-12)
    }

Notes:

None.