Sams Teach Yourself C# in 24 Hours

By James Foxall and Wendy Haro-Chun

• Table of Contents
  • Copyright
  • About the Authors
  • Acknowledgments
  • Tell Us What You Think!
  • Introduction
  • Audience and Organization
  • Conventions Used in This Book
  • Onward and Upward!
  • Part I. The Visual Studio Environment
  • Hour 1. A C# Programming Tour
  • Hour 2. Navigating C#
  • Hour 3. Understanding Objects and Collections
  • Hour 4. Understanding Events
  • Part II. Building a User Interface
  • Hour 5. Building FormsPart I
  • Hour 6. Building FormsPart II
  • Hour 7. Working with the Traditional Controls
    • Displaying Static Text with the Label Control
    • Allowing Users to Enter Text Using a Text Box
    • Creating Buttons
    • Creating Containers and Groups of Option Buttons
    • Displaying a List with the List Box
    • Creating Drop-Down Lists Using the Combo Box
    • Summary
    • Q&A
    • Workshop
  • Hour 8. Advanced Controls
  • Hour 9. Adding Menus and Toolbars to Forms
  • Hour 10. Drawing and Printing
  • Part III. Making Things HappenProgramming!
  • Hour 11. Creating and Calling Methods
  • Hour 12. Using Constants, Data Types, Variables, and Arrays
  • Hour 13. Performing Arithmetic, String Manipulation, and Date/Time Adjustments
  • Hour 14. Making Decisions in C# Code
  • Hour 15. Looping for Efficiency
  • Hour 16. Debugging Your Code
  • Hour 17. Designing Objects Using Classes
  • Hour 18. Interacting with Users
  • Part IV. Working with Data
  • Hour 19. Performing File Operations
  • Hour 20. Controlling Other Applications Using Automation
  • Hour 21. Working with a Database
  • Part V. Deploying Solutions and Beyond
  • Hour 22. Deploying a Solution
  • Hour 23. Introduction to Web Development
  • Hour 24. The 10,000-Foot View
  • Appendix A. Answers to Quizzes/Exercises

Allowing Users to Enter Text Using a Text Box

A Label control is usually the best control for displaying text a user can't change. However, when you need to let users enter or edit text, the text box is the tool for the job. If you've ever typed information on a form, you've almost certainly used a text box. Add a new text box to your form now by double-clicking the TextBox item in the toolbox. Set the text box's properties as follows:

When you first create a new text box, its Text property is set to its default name (see Figure 7.2). Unfortunately, the Text property isn't automatically changed when you change the name of the text box (which you should always do), so I recommend that you clear out the Text property of new text boxes. Delete the text in the Text property now and notice that the text box appears empty on the form.

Figure 7.2 A new text box has its Text property set to its default name.

Although you'll probably want to clear the Text property of most of your text boxes at design time, understanding certain aspects of the text box is easier when a text box contains text. Set the text box's Text property to This is sample text. Remember to press Enter or Tab to commit your property change.

Specifying Text Alignment

Both the TextBox and the Label controls have a TextAlign property (as do many other controls). The TextAlign property determines the alignment of the text within the control—very much like the justification setting in a word processor. You can select from Left, Center, or Right.

Change the TextAlign property of the text box to Right, and see how the text becomes right-aligned within the text box. Next, change TextAlign to Center to see what center alignment looks like. As you can see, this property is pretty straightforward. Change the TextAlign property back to Left before continuing.

Creating a Multiline Text Box

In the previous hour, I talked about the sizing handles of a selected control. I mentioned how handles that can be sized appear filled with white, and handles that are locked appear with a gray center. Notice how only the left and right edges of the text box have white sizing handles. This means that you can adjust only the left and right edges of the control (you can alter only the width, not the height). This is because the text box is defined as a single-line text box, meaning it will display only one line of text. What would be the point of a really tall text box that showed only a single line?

To allow a text box to display multiple lines of text, set its Multiline property to true. Set the Multiline property of your text box to true now, and notice that all the sizing handles become white.

Change the Text property of the text box to This is sample text. A multiline text box will wrap its contents as necessary. Press Enter or Tab to commit the property change. Notice how the text box displays only part of what you entered because the control simply isn't big enough to show all the text (see Figure 7.3). Change the Size property to 136,60, and you'll then see the entire content of the text box (see Figure 7.4).

Figure 7.3 A text box may contain more text than it can display.

Figure 7.4 A multiline text box can be sized as large as necessary.

At times, you won't want a user to be able to interact with a control. For instance, you may implement a security model in your application, and if the user doesn't have the necessary privileges, you may not want the user to be able to alter data. The Enabled property, which almost every control has, determines whether the user can interact with the control. Change the Enabled property of the text box to false, and press F5 to run the project. Although no noticeable change occurs in the control in Design view, there is a big change to the control at runtime: the text appears in gray rather than black, and the text box won't accept the focus or allow you to change the text (see Figure 7.5).

Figure 7.5 You can't interact with a text box whose Enabled property is set to false.

Stop the project now by choosing Stop Debugging from the Debug menu, and then change the control's Enabled property back to true.

Adding Scrollbars

Even though you can size a multiline text box, there may be times when the contents of the control are more than what can be displayed. If you believe that this is a possibility for a text box you're adding to a form, give the text box scrollbars by changing the ScrollBars property from None to Vertical, Horizontal, or Both.

Change the ScrollBars property of your text box to Vertical and notice how scrollbars appear in the text box (see Figure 7.6).

Figure 7.6 If a text box may contain lots of text, give it a scrollbar.

Limiting the Number of Characters a User Can Enter

You can limit the number of characters a user can type into a text box using the MaxLength property. All new text boxes are given the default value of 32767 for MaxLength, but you can change this as needed (up or down). Add a new text box to the form and set its properties as follows:

Run the project by pressing F5 and then enter the following text into the text box: So you run and you run. Be sure to try to enter more than 10 characters of text—you can't (if you can, you're probably entering the text into the text box with scrollbars, rather than into the new text box). All that you're allowed to enter is So you run (10 characters). The text box allows only 10 characters, whether that's via entry using the keyboard or a Paste operation. The MaxLength property is most often used when the text box's content is to be written to a database, in which field sizes are usually restricted (using a database is discussed in Hour 21, "Working with a Database").

Stop the project by choosing Stop Debugging from the Debug menu and then click Save All on the toolbar.

Creating Password Fields

You've probably used a password field: a text box that displays an asterisk for each character entered. Any text box can be made a password field by assigning a character to its PasswordChar field. Select the PasswordChar property of the second text box now (txtRestrict) and enter an asterisk (*) for the property value. Run the project once more and enter text into the text box. Now an asterisk is displayed for each character you enter (see Figure 7.7). Although the user doesn't see the actual text contained in the text box, referencing the Text property in code always returns the true text.

Figure 7.7 A password field displays its password character for all entered text.

Stop the project by choosing Stop Debugging from the Debug menu. Delete the asterisk from the PasswordChar field, and then save the project by clicking Save All on the toolbar.

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