Asking about global variable using VB.NET Window Form Application
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I'm new to VB.NET, currently I'm learning programming here. I have a Window Form(e.g. FrmLogin.vb) and a module which used to run the program (e.g. Module1.vb). I have declared a few public string variable as follow:
Option Explicit On
Imports System.Data
Imports System.Data.Odbc
Imports System.ConfigurationModule Module1
'User detail variable
Public UserID As String
Public UserName As String
Public UserPassword As String
End ModuleAnd I used the FrmLogin to verify the user by connecting to MySQL database. After the user successful login,I will set the UserID,UserName and UserPassword data load from the database which need to be used in my program for the future identification. But when I open another new form I found that these public variable is no value. Can anyone tell me how should I share a public variable inside VB.NET? This data will be used by alot of Form inside this application. Thank you for reading. Regards Drexler
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I'm new to VB.NET, currently I'm learning programming here. I have a Window Form(e.g. FrmLogin.vb) and a module which used to run the program (e.g. Module1.vb). I have declared a few public string variable as follow:
Option Explicit On
Imports System.Data
Imports System.Data.Odbc
Imports System.ConfigurationModule Module1
'User detail variable
Public UserID As String
Public UserName As String
Public UserPassword As String
End ModuleAnd I used the FrmLogin to verify the user by connecting to MySQL database. After the user successful login,I will set the UserID,UserName and UserPassword data load from the database which need to be used in my program for the future identification. But when I open another new form I found that these public variable is no value. Can anyone tell me how should I share a public variable inside VB.NET? This data will be used by alot of Form inside this application. Thank you for reading. Regards Drexler
From version 7 (VB.NET 2003) VB is an object oriented language, which means that there are no longer any global variables. All variables are either members of a class or local in a method. To set up variables that you can use like you did use global variables, you can use static variables. You use the Shared keyword to do this, and those variables are members of a class rather than members of an instance of the class.
Public Class UserDetails
Public Shared UserId As String
Public Shared UserName As String
Public Shared UserPassword As String
End ClassYou can access the variables from anywhere by specifying the class name and the variable name:
UserDetails.UserId = "42"Despite everything, the person most likely to be fooling you next is yourself.
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From version 7 (VB.NET 2003) VB is an object oriented language, which means that there are no longer any global variables. All variables are either members of a class or local in a method. To set up variables that you can use like you did use global variables, you can use static variables. You use the Shared keyword to do this, and those variables are members of a class rather than members of an instance of the class.
Public Class UserDetails
Public Shared UserId As String
Public Shared UserName As String
Public Shared UserPassword As String
End ClassYou can access the variables from anywhere by specifying the class name and the variable name:
UserDetails.UserId = "42"Despite everything, the person most likely to be fooling you next is yourself.
Hello Guffa, Do you mean that I should create all the public share variable into one main module,so all the form can use all the data inside this main module? And how can I insert or retrieve the data of UserID when I need it in other form from this class? Hope to get some solution about this from you all. Thank you~!
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Sorry Ashfield, What I need is declaring a variable for global used in my Vb.NET Window Form Application. I am trying to declare the global variable inside a Module1.vb. I have a few forms that using this global varaiable and it doesn't really works. Anyone could tell me how to declare a global variable which can share the variable used in all other different forms or class? Regards Drex
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Hello Guffa, Do you mean that I should create all the public share variable into one main module,so all the form can use all the data inside this main module? And how can I insert or retrieve the data of UserID when I need it in other form from this class? Hope to get some solution about this from you all. Thank you~!
Modules is something that for some reason survived from VB6. A module is compiled into a class where all the members are static, so if you declare variables in a module, you should be able to access them from anywhere.
Despite everything, the person most likely to be fooling you next is yourself.
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Modules is something that for some reason survived from VB6. A module is compiled into a class where all the members are static, so if you declare variables in a module, you should be able to access them from anywhere.
Despite everything, the person most likely to be fooling you next is yourself.
Yeah,thanks Guffa. Can you give me some idea how should I declare the variable of my Window Form Application? Let me further explain my situation below:
Option Explicit On
Imports System.Data
Imports System.Data.Odbc
Imports System.ConfigurationModule Module1
'User detail variable
Public UserID As String
Public UserName As String
Public UserPassword As String
End ModuleThis is how I test my retrieve data using Form from the varaiable in Module1.vb:
Messagebox.show(UserID)
Messagebox.show(UserName)
Messagebox.show(UserPassword)But all the messagebox prompup is Nothing. So,anyone can tell me how should I declare my variable so I can used anywhere in my project? The UserID,Username and Password is used for verification when working with certain function or task. Thank you for reading. Regards Drexler
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Yeah,thanks Guffa. Can you give me some idea how should I declare the variable of my Window Form Application? Let me further explain my situation below:
Option Explicit On
Imports System.Data
Imports System.Data.Odbc
Imports System.ConfigurationModule Module1
'User detail variable
Public UserID As String
Public UserName As String
Public UserPassword As String
End ModuleThis is how I test my retrieve data using Form from the varaiable in Module1.vb:
Messagebox.show(UserID)
Messagebox.show(UserName)
Messagebox.show(UserPassword)But all the messagebox prompup is Nothing. So,anyone can tell me how should I declare my variable so I can used anywhere in my project? The UserID,Username and Password is used for verification when working with certain function or task. Thank you for reading. Regards Drexler
It looks like you have declared your variables correctly, the reason the messagebox is showing nothing is becasue you haven't assigned them a value. Try UserID = "12345" Messagebox.Show(UserID)
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It looks like you have declared your variables correctly, the reason the messagebox is showing nothing is becasue you haven't assigned them a value. Try UserID = "12345" Messagebox.Show(UserID)
Yeah,thanks Liqs. I have solve it by converting the data to string instead of boolean when I assign into the variable. This solve my problem,thank you my friend. Regards :) Drex
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Modules is something that for some reason survived from VB6. A module is compiled into a class where all the members are static, so if you declare variables in a module, you should be able to access them from anywhere.
Despite everything, the person most likely to be fooling you next is yourself.
Yeah,thanks Guffa. I have solve it by converting the data to string instead of boolean when I assign into the variable. This solve my problem,thank you my friend. Regards Drex
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Yeah,thanks Guffa. I have solve it by converting the data to string instead of boolean when I assign into the variable. This solve my problem,thank you my friend. Regards Drex
So the problem was not at all in the code that you posted, but in some other code that you didn't post... Assigning a boolean value to a string variable is such an obvious error. I wonder why I didn't see that by looking at the code that you posted? ;)
Despite everything, the person most likely to be fooling you next is yourself.