OBJECTS and CLASSES.pdf - Objects and classes in Visual...

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9/2/2019 Objects and classes in Visual Basic | Microsoft Docs 1/10 Objects and classes in Visual Basic 07/20/2015 11 minutes to read +4 In this article Objects and classes Object members Reusing classes and objects Relationships among objects Related topics An object is a combination of code and data that can be treated as a unit. An object can be a piece of an application, like a control or a form. An entire application can also be an object. When you create an application in Visual Basic, you constantly work with objects. You can use objects provided by Visual Basic, such as controls, forms, and data access objects. You can also use objects from other applications within your Visual Basic application. You can even create your own objects and define additional properties and methods for them. Objects act like prefabricated building blocks for programs — they let you write a piece of code once and reuse it over and over. This topic discusses objects in detail. Objects and classes Each object in Visual Basic is defined by a class . A class describes the variables, properties, procedures, and events of an object. Objects are instances of classes; you can create as many objects you need once you have defined a class. To understand the relationship between an object and its class, think of cookie cutters and cookies. The cookie cutter is the class. It defines the characteristics of each cookie, for example size and shape. The class is used to create objects. The objects are the cookies. You must create an object before you can access its members. To create an object from a class
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9/2/2019 Objects and classes in Visual Basic | Microsoft Docs 2/10 1. Determine from which class you want to create an object. 2. Write a Dim Statement to create a variable to which you can assign a class instance. The variable should be of the type of the desired class. VB Copy 3. Add the New Operator keyword to initialize the variable to a new instance of the class. VB Copy 4. You can now access the members of the class through the object variable. VB Copy Multiple instances Objects newly created from a class are often identical to each other. Once they exist as individual objects, however, their variables and properties can be changed independently of the other instances. For example, if you add three check boxes to a form, each check box object is an instance of the CheckBox class. The individual CheckBox objects share a common set of characteristics and capabilities (properties, variables, procedures, and events) defined by the class. However, each has its own name, can be separately enabled and disabled, and can be placed in a different location on the form.
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