I'm creating a new Vb.Net project and I'm looking to create a module that will fire up when project is run so that the connection is set. I created a new module called Connection and placed the following code there...
Imports System.Data.SqlClient
Module Connection
Sub main()
Dim sConnection As String = "Data Source=Van;Initial Catalog=OP;User ID=userid;Password=password"
End Sub
End Module
And now in my Form1 I added the SQLConnection component and attempt to do something like this....
Using Con as New SQLConnection(sConnection)
'but this does not seem to work. The connection string works properly since it's fully working if I include it in the form itself.
Any particular reason why this is happening? Also, say I have 30 forms in the app, do I need to add the SqlConnection component to each form that will need to talk to the DB?
The "Main()" is a function.
And you declared a local variable "sConnection".
Your Form is another class.
A class can access only its members, global members or global static members (or some friend scenarios like C++).
Take out that declaration from "Main", either declare in the scope of your Form or declare it as a global variable, where your form can access.
Or put your connection string in a config file and read from it. (easy to configure at later point of time.)
Related
I know this appears to be a rather common topic and should have been resolved from earlier posts. But what I am experiencing still does not seem to have a solution online:
I have a form called ExpenseEntry in which there is a sub procedure called Public Sub OpenVoucher.
I want to call this sub from another form for which I use the following code:
Dim ExpForm As New ExpenseEntry
ExpForm.Show()
ExpForm.OpenVoucher()
While this works well enough, the problem is everytime I click the button, a new window of ExpenseEntry is launched. As per how I have designed the application, repeat windows is not permissible and only one window should be available at a time.
I have tried various methods to restrict more than one form such as by using a variable to control the form but that gives rise to other issues.
If I use Application.OpenForms but still does not resolve the issue.
I have earlier queried in this regard in the following link:
Textbox not refreshing
I am using VB.NET 2019 which does not allow the launch of default instance of a form like Form.Show. I know this is bad practice but it was easier to manage with that till VB.NET 2017.
Now by creating a form variable and launching that creates an infinite loop where I cannot have just one instance of a form running on a single thread.
The really simple way to handle this is to use the default instance of the form type. In VB, since 2005, each form type has a default instance that you can access via the type name. Read here for more info. In your case, you can do this:
'Display the form if it is not already displayed.
ExpenseEntry.Show()
'Activate the form if it is already displayed.
ExpenseEntry.Activate()
'Do the deed.
ExpenseEntry.OpenVouncher()
That said, default instances are a bit dodgy. They do enable beginners to access forms from anywhere in their project under certain circumstances but they also have limitations that can cause issues. Most importantly though, they help to prevent you learning proper OOP by treating forms differently to other types. If you want to do this the way a proper developer would then simply declare a variable to refer to the current instance of the form:
Private expenseEntryDialogue As ExpenseEntry
When it's time to use the form, you simply check whether that variable refers to a usable instance and use it if it does, otherwise create a new one:
If expenseEntryDialogue Is Nothing OrElse expenseEntryDialogue.IsDisposed Then
expenseEntryDialogue = New ExpenseEntry
End If
expenseEntryDialogue.Show()
expenseEntryDialogue.Activate()
expenseEntryDialogue.OpenVoucher()
A third option would be to implement your own singleton, i.e. a type that can only ever have a single instance. You probably wouldn't do that in VB, given that the default instance is basically a thread-specific singleton and does more automatically but, if you wanted to, you could do this:
Public Class ExpenseEntry
Private Shared _instance As ExpenseEntry
'The one and only instance of the type.
Public Shared ReadOnly Property Instance As ExpenseEntry
Get
If _instance Is Nothing OrElse _instance.IsDisposed Then
_instance = New ExpenseEntry
End If
Return _instance
End Get
End Property
'The constructor is private to prevent external instantiation.
Private Sub New()
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
End Sub
End Class
and then this:
ExpenseEntry.Instance.Show()
ExpenseEntry.Instance.Activate()
ExpenseEntry.Instance.OpenVoucher()
I have 20+ MDI forms with consistently named Public variables. When the child form closes a method on the MDI Parent is called passing Me as a generic form type. How can I access the public variables by name via the Form reference? I only need to read the variables. Of course the Variables() method does not exist...
Public Sub CleanupForm(ByVal frm As Form)
Dim sTable_Name As String = frm.Variables("TABLE_NAME") ' Public at form level
Dim cLock As clsRecLocks
cLock = frm.Variables("Rec_Lock")
cLock.DeleteThisLock()
'..
I've seen some posts on similar requests but most start out with "don't do it that way..." then go off in the weeds not answering the question. I concede it is poor design. I can't change all the calling forms in the short term so I need to use this approach.
VS2010, VB.Net, Win Forms, .Net 2.0
I was able to get to a simple variable using CallByName:
Try
Dim s As String = CallByName(frm, "TABLE_NAME", CallType.Get)
Stop
Catch ex As Exception
MsgBox(ex.Message)
End Try
On to the class object. Perhaps I can add a default Get for the class that returns the ID I need.
Default property won't work as the Locks object was not declared Public - at least for the CallByName() approach.
Can Reflection get to form level variables not declared Public? Seems like a security issue, but...
Can I get a "Parent" reference in the instantiated Locks class? i.e. A reference to the form that established the Locks object? I can change the clsRecLocks() class.
I found a property I could get to that told me the form was "read-only" and I can use that tidbit to delete the correct (or more correct - still not 100%) lock record. So the bug is 90% fixed. I think I need update all the forms with code that records the info I need to get to 100%.
Thanks to all!
Poor design but you can do this:
Public Sub CleanupForm(ByVal frm As Form)
Dim frmTest as object = frm
? = frmTest.TABLE_NAME
? = frmTest.Rec_Lock
End Sub
This will compile and if the variables exist, it will return them but if not, you get an error.
Converting to an interface after the fact is not that hard, you should do it now rather than later.
I have a VBA template project that runs automatically when a Word document is opened. However, if I open multiple documents, they all share the variables values. How can declare these variables to be only associated with the active window or active document?
I tried declaring them in a Class Module, but that did not help. Switching between opened document I can see that these variables are shared.
Any input is appreciated...
This what I have in my Module:
Option Private Module
Dim CurrentCommand As String
Public Function SetCurrentCommand(command)
CurrentCommand = command
End Function
Public Function GetCurrentCommand()
GetCurrentCommand = CurrentCommand
End Function
More Info: The code/Macro start at AutoExec like this:
Public Sub Main()
Set oAppClass.oApp = Word.Application
If PollingRate <> "" Then Application.OnTime Now + TimeValue(PollingRate), "CaptureUserViewState"
End Sub
And the CaptureUserViewState is a Sub that resides in a different Module and does all teh checks (comparing new values to last recorded ones) and here how this Sub does the check:
If WL_GetterAndSetter.GetLastPageVerticalPercentage <> pageVerticalPercentScrolled Then
'Update the last value variable
WL_GetterAndSetter.SetLastPageVerticalPercentage (pageVerticalPercentScrolled)
'log change
End If
You don't give us much information, but I assume you declared public variables at module level like this:
Public myString As String
Public myDouble As Double
From VBA documentation:
Variables declared using the Public statement are available to all procedures in all modules in all applications unless Option Private Module is in effect; in which case, the variables are public only within the project in which they reside.
The answer is to use Option Private Module.
When used in host applications that allow references across multiple projects, Option Private Module prevents a module’s contents from being referenced outside its project.
[...] If used, the Option Private statement must appear at module level, before any procedures.
EDIT You have now clarified that you declare your variables using Dim at module level. In this case, Option Private Module is irrelevant.
Variables declared with Dim at the module level are available to all procedures within the module.
i.e. regardless of whether you're using Option Private Module or not.
If you're finding that the values are retained between runs, then that must be because you are running a procedure from the same module from the same workbook. You may think you're doing something else, but in reality this is what you're doing.
EDIT
In your class module, instead of Dim CurrentCommand As String try Private CurrentCommand As String. Without more information it's hard to debug your program. I'm just taking random potshots here.
What you need to do is store multiple versions of the variables, one set per document.
So I would suggest that you create a simple class to hold the different values.
You then store them in a collection mapping the data-set with the document name or similar as the key.
In classmodule (MyData), marked as public:
Public data1 as String
Public data2 as Integer
In module with the event-handlers:
Dim c as new Collection 'module global declaration
Sub AddData()
Dim d as new MyData 'Your data set
d.data1 = "Some value"
d.data2 = 42
c.add Value:=d, Key:=ActiveDocument.name
End Sub
Then when you enter the event-handler you retrieve the data and use the specific set for the currently active document.
Sub EventHandler()
Dim d as MyData
set d = c.item(ActiveDocument.name)
'use data
'd.data1...
End Sub
Please not that this code is just on conceptual level. It is not working, You have to apply it to your problem but it should give you some idea on what you need to do. You will need to add alot of error handling, checking if the item is already in the collection and so on, but I hope you understand the concept to continue trying on your own.
The reason for this is because, as I understand the situation from your question, you only have one version of your script running, but multiple documents. Hence the script have to know about all the different documents.
On the other hand, If each document would have their own code/eventhandlers, hence having multiple versions of the script running, then you don't need the solution provided above. Instead you need to be careful what document instance you reference in your script. By always using "ThisDocument" instead of "ActiveDocument" you could achieve isolation if the code is placed in each open document.
However, as I understood it, you only have one version of the script running, separate from the open documents, hence the first solution applies.
Best of luck!
You might want to store the Document Specific details using
The Document.CustomDocumentProperties Property
http://msdn.microsoft.com/en-us/library/office/aa212718(v=office.11).aspx
This returns a
DocumentProperties Collection
Which you can add new Properties to Using
Document.CustomDocumentProperties.Add(PropertyName, LinkToContent, Value, Type)
And then Read From using
Document.CustomDocumentProperties.Item(PropertyName)
A downside, or bonus, here is that the properties will remain stored in the document unless you delete them.
This may be a good thing or a bad thing
vb.net windows forms question.
I've got 3 forms that have exactly the same functions, so I decided to create an interface.
public Interface IExample
public sub Add()
Public sub Edit()
Public sub View()
End Interface
Then I created the 3 forms, and added the 'implements interface IExample' to each.
public class frmExample1
implements Interface IExample
Same for frmExample2, frmExample3
Finally, in code, I declare a variable of the interface type ..
Dim objfrmExample as IExample
then ...
objFrmExample = frmExample2
At this point, objfrmExample is now instantiated, even though I've not done a "objfrmExpample = new [what-goes-here?] " and I'm curious as to why.
I could possibly guess that because you cannot instantiate an interface variable, then vb.net automatically creates an instance. But thats just a guess. The question is , what is meant by declaring a variable of type Interface, and how does it work?
Anyway, just curious :-)
At this point, objfrmExample is now instantiated, even though I've not done a "objfrmExpample = new [what-goes-here?] " and I'm curious as to why.
This has nothing to do with interfaces. You can always treat a form class name in VB as though it were an instance. The reason is that the VB compiler creates properties of all your forms inside My.Forms. Now you can access a “default” instance of each form by accessing My.Forms.<FormName>.
Now comes the ugly part: you can also omit My.Forms.. In other words, whenever you write just FormName and from the context it’s unambiguous that you need an instance rather than the class name, VB will act as though you’d written My.Forms.<FormName>.
Luckily, this only works for forms, not for any other classes. VB creates each default instance when you first access it. So as long as you don’t access a default instance, it’s not created. Once you access it for the first time, VB creates it and invokes its constructor.
When you declare a variable of type interface you can work with any object that implements the interface. Therefore when setting a variable that is of an interface type equal to a class that implements the interface an implicit cast is done. For example.
Dim oExample as IExample
dim testForm as MyTestForm
oExample = MyTestForm
Now, this is the way that you do it, you can do an explicit cast this way
Dim oExample as IExample
Dim testForm as MyTestForm
oExample = CType(MyTestForm, IExample)
For your specific example with VB.NET and an un-instantiated form this is due to a VB "feature" that auto-creates an instance of the form.
You can change the connection string at run-time like this. You make the connection string setting available for writing as a separate property inside the MySettings class:
Partial Friend NotInheritable Class MySettings
Public WriteOnly Property RunTimeConnectionString()
Set(ByVal value)
My.Settings("MyConnectionString") = value
End Set
End Property
End Class
Then, in some place when the application is being initialized (before using any table adapters of typed datasets), write something like:
My.Settings.RunTimeConnectionString = My.Settings.ProductionConnectionString
Where ProductionConnectionString is a simple String setting. It is a User Scope setting so every user can change it (by assigning a value to it, similar to the code above) and save it by calling My.Settings.Save()
This code works well for connection strings which were initially created in the main project and stored in it's settings (= app.config file).
The connection string in the app.config actually has a longer name: MyApp.MySettings.MyConnectionString.
When you have a connection string stored in the app.config in a class library project, and reference that project in the main project, the app.config files will somehow be merged, so the class library has it's settings.
The thing that don't know how to do, is change a setting from the class library at run-time. I could copy the connection string setting from the class library to the main project's app.config. I must keep the same name, which looks something like: MyClassLibrary.My.MySettings.MyConnectionString.
Can the same principle I showed above be somehow applied to this second connection string?
I tested a little more, and found out that the same solution can be used inside a class library.
I made a new class (in the class library) with a shared (static) method like this:
Public Class MySettingsChanger
Public Shared Sub SetConnectionString(ByVal cnnString As String)
My.Settings.RunTimeConnectionString = cnnString
End Sub
End Class
And extended the MySettings class (in the class library) the same way as in the main project:
Namespace My
Partial Friend NotInheritable Class MySettings
Public WriteOnly Property RunTimeConnectionString()
Set(ByVal value)
My.Settings("MyConnectionString") = value
End Set
End Property
End Class
End Namespace
At least it works in my case. The name of the connection in the main project and in the class library is the same only (the short name, not the whole ProjectNamespace.MySettings.ConnectionName). I haven't tested with having a different name of the connection in the class library, but think it should not matter.
I searched more, and found a way, but it isn't really runtime. At least not as runtime as I would like it to be. Anyway, here is the code, I tested it and it worked, but required me to restart the application first. That's not very runtime to me.
Dim configLocation As String = Reflection.Assembly.GetExecutingAssembly().Location
Dim config As Configuration.Configuration = Configuration.ConfigurationManager.OpenExeConfiguration(configLocation)
config.ConnectionStrings.ConnectionStrings.Clear()
For i As Integer = 0 To Configuration.ConfigurationManager.ConnectionStrings.Count - 1
Dim connection As New Configuration.ConnectionStringSettings(Configuration.ConfigurationManager.ConnectionStrings(i).Name, My.Settings.ProductionConnectionString)
connection.ProviderName = Configuration.ConfigurationManager.ConnectionStrings(i).ProviderName
config.ConnectionStrings.ConnectionStrings.Add(connection)
Next
config.Save()
This is the article where I found this code.
Thanks for the message on the blog. Yes, it is hardly run-time as it requires you to stop running for the changes to be picked up. Unfortunately, because settings are loaded once and only once (when the app domain is loaded), there isn't a way for the settings infrastructure to pick up changes while running.
The only option is to either restart the app or recyle the app pool if a web application. Beyond that, you would have to roll your own.
I did the best I could :-)