Classes vs Modules in VB NET

Question

Is it considered an acceptable practice to use Modules instead of Classes with Shared member functions in VB NET   I tend to avoid Modules  because they feel like leftover remains from Visual Basic 6 0 and don t really seem to fit in anymore  On the other hand  there doesn t seem to be much difference between using a Module and a Class with only Shared members  It s not that often that I really have much need for either  but sometimes there are situations where they present a simple solution   I m curious to hear whether you have any opinion or preferences one way or the other

User · Answer

It is acceptable to use Module  Module is not used as a replacement for Class  Module serves its own purpose  The purpose of Module is to use as a container for   extension methods  variables that are not specific to any Class  or variables that do not fit properly in any Class    Module is not like a Class since you cannot   inherit from a Module  implement an Interface with a Module  nor create an instance of a Module    Anything inside a Module can be directly accessed within the Module assembly without referring to the Module by its name  By default  the access level for a Module is Friend

User · Answer

When one of my VB NET classes has all shared members I either convert it to a Module with a matching  or otherwise appropriate  namespace or I make the class not inheritable and not constructable   Public NotInheritable Class MyClass1     Private Sub New          Contains only shared members         Private constructor means the class cannot be instantiated     End Sub  End Class

User · Answer

Modules are by no means deprecated and are used heavily in the VB language   It s the only way for instance to implement an extension method in VB Net   There is one huge difference between Modules and Classes with Static Members   Any method defined on a Module is globally accessible as long as the Module is available in the current namespace   In effect a Module allows you to define global methods   This is something that a class with only shared members cannot do    Here s a quick example that I use a lot when writing VB code that interops with raw COM interfaces   Module Interop   Public Function Succeeded ByVal hr as Integer  As Boolean           End Function    Public Function Failed ByVal hr As Integer  As Boolean           End Function End Module  Class SomeClass   Sub Foo       Dim hr   CallSomeHrMethod       if Succeeded hr  then              End If   End Sub End Class

User · Answer

Modules are VB counterparts to C  static classes  When your class is designed solely for helper functions and extension methods and you don t want to allow inheritance and instantiation  you use a Module   By the way  using Module is not really subjective and it s not deprecated  Indeed you must use a Module when it s appropriate   NET Framework itself does it many times  System Linq Enumerable  for instance   To declare an extension method  it s required to use Modules

User · Answer

I think it s a good idea to keep avoiding modules unless you stick them into separate namespaces  Because in Intellisense methods in modules will be visible from everywhere in that namespace   So instead of ModuleName MyMethod   you end up with MyMethod   popups in anywhere and this kind of invalidates the encapsulation   at least in the programming level    That s why I always try to create Class with shared methods  seems so much better

User · Answer

Modules are fine for storing enums and some global variables  constants and shared functions  its very good thing and I often use it  Declared variables are visible acros entire project

User · Answer

Classes   classes can be instantiated as objects  Object data exists separately for each instantiated object  classes can implement interfaces  Members defined within a class are scoped within a specific instance of the class and exist only for the lifetime of the object  To access class members from outside a class  you must use fully qualified names in the format of Object Member    Modules   Modules cannot be instantiated as objects Because there is only one copy of a standard module s data  when one part of your program changes a public variable in a standard module  it will be visible to the entire program  Members declared within a module are publicly accessible by default  It can be accessed by any code that can access the module   This means that variables in a standard module are effectively global variables because they are visible from anywhere in your project  and they exist for the life of the program

User · Answer

You must use a Module  rather than a Class  if you re creating Extension methods  In VB NET I m not aware of another option   Being resistant to Modules myself  I just spent a worthless couple of hours trying to work out how to add some boilerplate code to resolve embedded assemblies in one  only to find out that Sub New    Module  and Shared Sub New    Class  are equivalent   I didn t even know there was a callable Sub New   in a Module    So I just threw the EmbeddedAssembly Load and AddHandler AppDomain CurrentDomain AssemblyResolve lines in there and Bob became my uncle   Addendum  I haven t checked it out 100  yet  but I have an inkling that Sub New   runs in a different order in a Module than a Class  just going by the fact that I had to move some declarations to inside methods from outside to avoid errors

[vb.net] Classes vs. Modules in VB.NET

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