![]() However, you may still need destructors to clean up any unmanaged resources that your application creates. NET Framework, the garbage collector automatically manages the allocation and release of memory for the managed objects in your application. Destructorsĭestructors are used to destruct instances of classes. To define a constructor for a class: Class SampleClassįor more information, see: Object Lifetime: How Objects Are Created and Destroyed. However, you can create multiple constructor overloads in the same way as for any other method. ![]() Furthermore, the code in the constructor always runs before any other code in a class. ![]() A constructor can run only once when a class is created. Constructors usually initialize the data members of the new object. However, Visual Basic also supports extension methods that allow you to add methods to an existing class outside the actual definition of the class.Ĭonstructors are class methods that are executed automatically when an object of a given type is created. In most cases you declare a method within a class definition. Overloads Sub Display(ByVal theInteger As Integer) To overload a method: Overloads Sub Display(ByVal theChar As Char) Public Function SampleFunc(ByVal SampleParam As String)Ī class can have several implementations, or overloads, of the same method that differ in the number of parameters or parameter types. To define a method of a class: Class SampleClass In Visual Basic, there are two ways to create a method: the Sub statement is used if the method does not return a value the Function statement is used if a method returns a value. However, auto-implemented properties cannot be read-only or write-only.Ī method is an action that an object can perform. In Visual Basic you can use ReadOnly and WriteOnly keywords. However, you can create read-only or write-only properties to restrict them from being modified or read. Most properties have methods or procedures to both set and get the property value. If you need to perform some additional operations for reading and writing the property value, define a field for storing the property value and provide the basic logic for storing and retrieving it: Class SampleClass To define an auto-implemented property: Class SampleClass Visual Basic allows you either to create a private field for storing the property value or use so-called auto-implemented properties that create this field automatically behind the scenes and provide the basic logic for the property procedures. Properties have get and set procedures, which provide more control on how values are set or returned. Fields are like variables because they can be read or set directly. Properties and fieldsįields and properties represent information that an object contains. To define a structure: Structure SampleStructureĮach class can have different class members that include properties that describe class data, methods that define class behavior, and events that provide communication between different classes and objects. Visual Basic also provides a light version of classes called structures that are useful when you need to create large array of objects and do not want to consume too much memory for that. Using the blueprint analogy, a class is a blueprint, and an object is a building made from that blueprint. So, the act of creating an object is called instantiation. The terms class and object are sometimes used interchangeably, but in fact, classes describe the type of objects, while objects are usable instances of classes. This section describes the following concepts: Polymorphism means that you can have multiple classes that can be used interchangeably, even though each class implements the same properties or methods in different ways. Inheritance describes the ability to create new classes based on an existing class. Visual Basic provides full support for object-oriented programming including encapsulation, inheritance, and polymorphism.Įncapsulation means that a group of related properties, methods, and other members are treated as a single unit or object.
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