Topic group

All objects on a form exist in layers. When a form contains two or more controls, the plane in which a control exists always lies in front of or behind the plane in which another control exists. This affects two aspects of the form:

Visual layers, or the z-order, which indicates the z-axis (depth) of the layout. This determines what appears in front of (or on top of) what. Even when controls are laid out side-by-side, each control is in a unique plane of the form. That is, each control occupies a unique position in the z-order.

Tabbing order, which determines the order in which controls receive focus when a user presses Tab (focus moves forward along the z-order) or Shift-Tab (focus moves backward along the z-order).

Each control is numbered to indicate its z-order position. The item in the back is number 1. The next item in front of the first item is number 2, and so on. By default, the z-order is the same as the order in which you added controls to the form. However, this is probably not the tab order you want. By choosing View|Order View, you can see the order of controls on a form and change the order by clicking on the numbers. Another way to change the order is to choose Layout|Set Component Order.

Another need for z-ordering is when you use a rectangle control, for example, to group a series of RadioButtons. The RadioButtons must appear on top of the rectangle, so you need to place the rectangle behind them in the z-order.