That article on MSDN is about the TextBox class that is part of the .NET Framework which is NOT the WinAPI (same applies to the richtext editor). However, text boxes are probably part of the WinAPI as well but you won't be able to use them inside a DirectX instance. You will have to write your own textbox class that is rendered by the engine. Open/Save dialogues are part of the WinAPI and can easily be used (but don't confuse them with their counterparts in the .NET Framework).