Visual Basic 2005 Demysti ed in Java

Recognizer DataMatrix in Java Visual Basic 2005 Demysti ed

The String and Char data types are used for text A string is simply one or more characters, usually enclosed in double quotes to indicate that a string is intended The characters may be alpha (A Z or a z), numeric (0 9), or virtually any other character you can type from your keyboard For example, the name R2D2 is a string even though it includes the numeric character 2 The String data type would be a good choice for the teacher s name, such as Genghis Khent, my students fond ( ) nickname for me The Char data type represents a single character, also enclosed in double quotes, followed by an upper- or lowercase c to indicate that it is a character rather than a string As with a string, the character may be alpha (A Z or a z), numeric (0 9), or virtually any other character you can type from your keyboard The Char data type would be a good choice for the grade you hope to earn in the class, such as an A There are other data types, some of which will be mentioned in later chapters However, these five data types, Integer, Double, String, Char, and Boolean, are the ones principally used

Take a look at the Properties window of the form in your project The form has many different properties These properties determine the form s height and width, background color, caption, visibility, and so on Visual Basic 2005 uses these properties when you start a project to determine the form s size, background color, and so forth Each of these properties stores a particular value The Height property stores a number that represents the height of the form The Text property stores a string that represents the title displayed by the form The Visible property stores a Boolean value that represents whether the form is visible (True) or hidden (False) You can access the values of many properties when designing your application (design time) simply by viewing them in the Properties window You also can access the values of many properties while your application is running through code (run time) In 2, we changed the Text property of the form at run time; in 3, we changed the Text property of labels at run time However, whether you are in design time or run time, the new value of a property must be of the correct data type To confirm this, in the Properties window of the form, type Jeff next to the Height property, which you can access by expanding the Size property, as shown in Figure 4-1 Then press ENTER A dialog box will display, as in Figure 4-2, warning you of an invalid property value

Click the Details button of the dialog box in Figure 4-2 The dialog box then will display the message, Jeff is not a valid value for Int32 As discussed previously, SystemInt32 is the name used in the NET Framework for the Integer data type That Visual Basic 2005 prevents you from changing the value of the Height property to Jeff makes sense The height must be a number Visual Basic does not know how to make a form of the height Jeff Try exploring the properties of the form in the Properties window You will see there are many different data types for the different properties

You can store, access, and change the value of a property However, you cannot change what the property stands for For example, the Height property of a Form object represents the height of a form; you cannot change that property so that it instead represents the width of a form or the name of your favorite ice cream Instead, you can create a variable to store data of your choosing, such as the name of your favorite ice cream, your social security number, and so on