A control is an object that can be drawn on to the Form to enable or enhance user interaction with the application. Examples of these controls, TextBoxes, Buttons, Labels, Radio Buttons, etc. All these Windows Controls are based on the Control class, the base class for all controls. Visual Basic allows us to work with controls in two ways: at design time and at runtime. Working with controls at design time means, controls are visible to us and we can work with them by dragging and dropping them from the Toolbox and setting their properties in the properties window. Working at runtime means, controls are not visible while designing, are created and assigned properties in code and are visible only when the application is executed. There are many new controls added in Visual Basic .NET and we will be working with some of the most popular controls in this section. You can select the controls from the menu towards the left-hand side of this page.
Notable properties of most of these Windows Controls which are based on the Control class itself are summarized in the table below. You can always find the properties of the control with which you are working by pressing F4 on the keyboard or by selecting View->Properties Window from the main menu.
The Control Class
The Control class is in the System.Windows.Forms namespace. It is a base class for the Windows Controls. The class hierarchy is shown below.
ButtonBase, Etc, Etc
Button, Etc, Etc
Main class is the Object class from which MarshalByRefObject class is derived and the Component class is derived from the MarshalByRefObject class and so on.
The properties of the Control object are summarized below. Properties are alphabetical as seen in the properties window.
Control Tab Order
To move focus from one control to other quickly using the keyboard we can use the Tab key. We can set the order in which the focus is transferred by setting the tab order. The tab order is the order in which controls on the form receive the focus and is specified by the TabIndex property. To change the order in which a control receives focus we need to set the TabIndex property to different value for each control on the form. Lower values receive the focus first and proceed numerically through higher values. If there is a tie between TabIndex values, the focus first goes to the control that is closest to the front of the form.
We can also set the tab order graphically with Visual Studio by selecting Tab Index from the View menu. Boxes containing current tab order appear in each control when you select Tab Index from View menu. Click each control to set the correct tab order in which you want the controls to receive focus.