C# Constants:

public class GetWindowConstants {

    public const uint GW_MIN = 0;
    public const uint GW_HWNDFIRST = 0;
    public const uint GW_HWNDLAST = 1;
    public const uint GW_HWNDNEXT = 2;
    public const uint GW_HWNDPREV = 3;
    public const uint GW_OWNER = 4;
    public const uint GW_CHILD = 5;
    public const uint GW_ENABLEDPOPUP = 6;
    public const uint GW_MAX = 6;

}

//Windows version <= 0x0400

public class GetWindowConstantsObsolete {

    public const uint GW_MIN = 0;
    public const uint GW_HWNDFIRST = 0;
    public const uint GW_HWNDLAST = 1;
    public const uint GW_HWNDNEXT = 2;
    public const uint GW_HWNDPREV = 3;
    public const uint GW_OWNER = 4;
    public const uint GW_CHILD = 5;
    public const uint GW_MAX = 5;

}

VB Constants:

Public Enum GetWndConsts

    GW_MIN = 0
    GW_HWNDFIRST = 0
    GW_HWNDLAST = 1
    GW_HWNDNEXT = 2
    GW_HWNDPREV = 3
    GW_OWNER = 4
    GW_CHILD = 5
    GW_ENABLEDPOPUP = 6
    GW_MAX = 6

End Enum

Notes:

Defined in Winuser.h.