Creating Drop-Down Lists Using the Combo Box

The first thing you should note is that the combo box has a Text property, whereas the list box doesn't. This works the same as the Text property of a text box. When the user selects an item from the drop-down list, the value of the selected item is placed in the Text property of the text box. The default behavior of a combo box is to allow the user to enter any text in the text box portion of the control ”even if the text doesn't exist in the list. Shortly, I'll show you how to change this behavior.

Select the Items property of the combo box in the Properties window and click the button that appears. Add the following items to the String Collection editor and click OK to commit your entries.

• Black

• Blue

• Gold

• Green

• Red

• Yellow

Press F5 to run the project. Click the arrow at the right side of the combo box and a drop-down list appears (see Figure 7.18).

Next, try typing in the text Magenta. C# lets you do this. Indeed, you can type any text that you desire . Often, you'll want to restrict a user to entering only values that appear in the list. To do this, you change the DropDownStyle property of the combo box. Close the form to stop the running project and change the DropDownStyle property of the combo box to DropDownList. Press F5 to run the project again and try to type text into the combo box. You can't. However, if you enter a character that is the start of a list item, C# will select the closest matching entry.

As a matter of fact, clicking in the "text box" portion of the combo box opens the list the same as if you clicked the drop-down arrow. When set as a DropDownList, a combo box won't allow any text entry; therefore, the user is limited to selecting items from the list.

Stop the running project now and save your work. As you can see, the combo box and list box offer similar functionality. In fact, the coding of their lists is identical. However, each one of these controls serves a slightly different purpose. Which one is better? That depends entirely on the situation. As you use professional applications, pay attention to their interfaces; you'll start to get a feel for which control is appropriate in a given situation.

Summary

In this hour you learned how to present text to a user. You learned that the Label control is perfect for displaying static text (text the user can't enter) and that the text box is the control to use for displaying edited text. You can now create text boxes that contain many lines of text, and you know how to add scrollbars when the text is greater than what can be displayed in the control.

I don't think I've ever seen a form without at least one button on it. You've now learned how to add buttons to your forms and how to do some interesting things, such as adding a picture to a button. For the most part, working with buttons is a simple matter of adding one to a form, settings its Name and Text properties, and adding some code to its Click event ”all of which you now know how to do.

Check boxes and option buttons are used to present true/false and mutually exclusive options, respectively. In this hour, you learned how to use each of these controls and how to use group boxes to logically group sets of related controls.

Last, you learned how to use list boxes and combo boxes to present lists of items to a user. You now know how to add items to a list at design time as well as runtime, and you know how to sort items. The List Box and Combo Box are powerful controls, and I encourage you to dig deeper into the functionality they possess.

Without controls, users would have nothing to interact with on your forms. In this hour, you learned how to use the standard controls to begin building functional interfaces. Keep in mind that I only scratched the surface of each of these controls and that most do far more than I've hinted at here. Mastering these controls will be easy for you, as you'll be using them a lot.