Orthographic Projection of 2D objects

I would like to know how to set the various parameters required to have an 2D object orthographically projected on to the window. I am using VB. I would like to receive code samples which can help me out. I am drawing a 2D-line diagram of an object using perspective projection due to which I am unable to get a realistic size-view of the object in the window. Plz send me code samples illustrating both perspective & orthographic projection on to the window.