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.