Declare global variables in Visual Studio 2010 and VB NET

Question

How do I declare a global variable in Visual Basic   These variables need to be accessible from all the Visual Basic forms  I know how to declare a public variable for a specific form  but how do I do this for all the forms in my project

User · Answer

Make it static  shared in VB    Public Class Form1     Public Shared SomeValue As Integer   5  End Class

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The first guy with a public class makes a lot more sense   The original guy has multiple forms and if global variables are needed then the global class will be better   Think of someone coding behind him and needs to use a global variable in a class you have IntelliSense  it will also make coding a modification 6 months later a lot easier   Also if I have a brain fart and use like in an example parts on a module level then want my global parts I can do something like  Dim Parts as Integer parts   3 GlobalVariables parts    Parts    lt  Not recommended but it works   At least that s why I would go the class route

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Pretty much the same way that you always have  with  Modules  instead of classes and just use  Public  instead of the old  Global  keyword   Public Module Module1     Public Foo As Integer End Module

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A global variable could be accessible in all your forms in your project if you use the keyword public shared if it is in a class  It will also work if you use the keyword  public  if it is under a Module  but it is not the best practice for many reasons        Yes  I somewhat repeating what  Cody Gray  and  RBarryYoung  said    One of the problems is when you have two threads that call the same global variable at the same time  You will have some surprises  You might have unexpected reactions if you don t know their limitations  Take a look at the post Global Variables in Visual Basic  NET and download the sample project

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Okay  I finally found what actually works to answer the question that seems to be asked    When needing many modules and forms  how can I declare a variable to be public to all of them such that they each reference the same variable    Amazingly to me  I spent considerable time searching the web for that seemingly simple question  finding nothing but vagueness that left me still getting errors   But thanks to Cody Gray s link to an example  I was able to discern a proper answer     Situation  You have multiple Modules and or Forms and want to reference a particular variable from each or all    A  way that works  On one module place the following code  wherein  DefineGlobals  is an arbitrarily chosen name     Public Module DefineGlobals  Public Parts As Integer                  Assembled-particle count Public FirstPrtAff As Long               Addr into Link List  End Module   And then in each Module Form in need of addressing that variable  Parts   place the following code  as an example of the  InitForm2  form    Public Class InitForm2 Private Sub InitForm Load ByVal sender As System Object  ByVal e As System EventArgs  Handles MyBase Load      Parts   Parts   3  End Sub  End Class   And perhaps another Form      Public Class FormX  Sub CreateAff       Parts   1000  End Sub    End Class   That type of coding seems to have worked on my VB2008 Express and seems to be all needed at the moment  void of any unknown files being loaded in the background  even though I have found no end to the  Oh btw     surprise details  And I m certain a greater degree of standardization would be preferred  but the first task is simply to get something working at all  with or without standards   Nothing beats exact and well worded  explicit examples   Thanks again  Cody

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small remark  I am using modules in webbased application  asp net   I need to remember that everything I store in the variables on the module are seen by everyone in the application  read website  Not only in my session  If i try to add up a calculation in my session I need to make an array to filter the numbers for my session and for others  Modules is a great way to work but need concentration on how to use it   To help against mistakes  classes are send to the     CarbageCollector   when the page is finished  My modules stay alive  as long as the application is not ended or restarted  and I can reuse the data in it  I use this to save data that sometimes is lost because of the sessionhandling by IIS      IIS Form auth   and     IIS session   are not in sync  and with my module I pull back data that went over de cliff

User · Answer

You could just add a new Variable under the properties of your project Each time you want to get that variable you just have to use  My Settings  Name of variable    That ll work for the entire Project in all forms

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All of above can be avoided by simply declaring a friend value for runtime on the starting form   Public Class Form1  Friend sharevalue as string    Boo    Then access this variable from all forms simply using Form1 sharevalue

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There is no way to declare global variables as you re probably imagining them in VB NET   What you can do  as some of the other answers have suggested  is declare everything that you want to treat as a global variable as static variables instead within one particular class   Public Class GlobalVariables     Public Shared UserName As String    Tim Johnson      Public Shared UserAge As Integer   39 End Class   However  you ll need to fully-qualify all references to those variables anywhere you want to use them in your code  In this sense  they are not the type of global variables with which you may be familiar from other languages  because they are still associated with some particular class   For example  if you want to display a message box in your form s code with the user s name  you ll have to do something like this   Public Class Form1  Inherits Form      Private Sub Form1 Load ByVal sender As Object  ByVal e As EventArgs  Handles Me Load         MessageBox Show  Hello     amp  GlobalVariables UserName      End Sub  End Class   You can t simply access the variable by typing UserName outside of the class in which it is defined   you must also specify the name of the class in which it is defined    If the practice of fully-qualifying your variables horrifies or upsets you for whatever reason  you can always import the class that contains your global variable declarations  here  GlobalVariables  at the top of each code file  or even at the project level  in the project s Properties window   Then  you could simply reference the variables by their name   Imports GlobalVariables   Note that this is exactly the same thing that the compiler is doing for you behind-the-scenes when you declare your global variables in a Module  rather than a Class  In VB NET  which offers modules for backward-compatibility purposes with previous versions of VB  a Module is simply a sealed static class  or  in VB NET terms  Shared NotInheritable Class   The IDE allows you to call members from modules without fully-qualifying or importing a reference to them  Even if you decide to go this route  it s worth understanding what is happening behind the scenes in an object-oriented language like VB NET  I think that as a programmer  it s important to understand what s going on and what exactly your tools are doing for you  even if you decide to use them  And for what it s worth  I do not recommend this as a  best practice  because I feel that it tends towards obscurity and clean object-oriented code design  It s much more likely that a C  programmer will understand your code if it s written as shown above than if you cram it into a module and let the compiler handle everything     Note that like at least one other answer has alluded to  VB NET is a fully object-oriented language  That means  among other things  that everything is an object  Even  global  variables have to be defined within an instance of a class because they are objects as well  Any time you feel the need to use global variables in an object-oriented language  that a sign you need to rethink your design  If you re just making the switch to object-oriented programming  it s more than worth your while to stop and learn some of the basic patterns before entrenching yourself any further into writing code

User · Answer

Public variables are a code smell - try to redesign your application so these are not needed  Most of the reasoning here and here are as applicable to VB NET   The simplest way to have global variables in VB NET is to create public static variables on a class  declare a variable as Public Shared

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None of these answers seem to be changing anything for me   I am converting an old Excel program to VB 2008  Of course  there are many Excel specific things to change  but something that is causing a headache seems to be this whole  Public  issue   I have about 40 arrays all being referenced by about 20 modules  The arrays form the foundation of the entire project and are addressed by just about every procedure   In Excel  I simply had to declare them all as Public  Worked great  No problem  But in VB2008  I m finding it quite an issue  It is absurd to think that I have to go through thousands of lines of code merely to tell each reference where the Public has been declared  But even willing to do that  none of the schemes being proposed seems to help at all   It appears that  Public  merely means  Public within this one module   Adding  Shared  seems to do nothing to change that  Adding the module name or anything else doesn t seem to change that  Each module insists that I declare all arrays  and about 100 other fundamental variables  within each module  a seemingly backward advance   And the  Imports  bit doesn t seem to know what I am talking about either   cannot be found    I have to sympathize with the questioner  Something seems terribly amiss with all of this

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The various answers in this blog seem to be defined by SE s who promote strict adherence to the usual rules of object-oriented programming  use a Public Class with public shared  aka static   and fully-qualified class references  or SE s who promote using the backward-compatibility feature  Module  for which the compiler obviously needs to do the same thing to make it work   As a SE with 30  years of experience  I would propose the following guidelines    If you are writing all new code  not attempting to convert a legacy app  that you avoid using these forms altogether except in the rare instance that you really DO need to have a static variable because they can cause terrible consequences  and really hard-to-find bugs    Multithread and multiprocessing code requires semaphores around static variables     If you are modifying a small application that already has a few global variables  then formulate them so they are not obscured by Modules  that is  use the standard rules of object-oriented programming to re-create them as public static and access them by full qualification so others can figure out what is going on  If you have a huge legacy application with dozens or hundreds of global variables  by all means  use Modules to define them  There is no reason to waste time when getting the application working  because you are probably already behind the 8-ball in time spent on Properties  etc

User · Answer

Public Class Form1     Public Shared SomeValue As Integer   5  End Class   The answer   MessageBox Show  this is the number  amp GlobalVariables SomeValue

[vb.net] Declare global variables in Visual Studio 2010 and VB.NET

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