Structures implicitly inherit from the System.ValueType class and cannot inherit from any other type classes can inherit from any class or classes other than System.ValueType. Structure variable declarations cannot specify initializers or initial sizes for arrays class variable declarations can. Structure elements cannot be declared as Protected class members can.Ī structure procedure can handle events only if it is a Shared Sub procedure, and only by means of the AddHandler Statement any class procedure can handle events, using either the Handles keyword or the AddHandler statement. This behavior for class members provides compatibility with the Visual Basic 6.0 system of defaults.Ī structure must have at least one nonshared variable or nonshared, noncustom event element a class can be completely empty. Structures use stack allocation classes use heap allocation.Īll structure elements are Public by default class variables and constants are Private by default, while other class members are Public by default. A variable of a structure type contains the structure's data, rather than containing a reference to the data as a class type does. Structures are value types classes are reference types. Structures and classes differ in the following particulars:

For example, one member can be declared Public and another Private.īoth can have shared constructors, with or without parameters.īoth can expose a default property, provided that property takes at least one parameter.īoth can declare and raise events, and both can declare delegates. Members of both can have individualized access levels. Structures and classes are similar in the following respects:īoth are container types, meaning that they contain other types as members.īoth have members, which can include constructors, methods, properties, fields, constants, enumerations, events, and event handlers. Use structures when the object you wish to create has a small instance size, and take into account the performance characteristics of classes versus structures. On the other hand, structures do not require allocation of memory on the global heap.īecause you cannot inherit from a structure, structures should be used only for objects that do not need to be extended.

However, there are also important differences between structures and classes.Ĭlasses have the advantage of being reference types - passing a reference is more efficient than passing a structure variable with all its data. Visual Basic unifies the syntax for structures and classes, with the result that both entities support most of the same features.

Visual basic data structure