I would like to know how to pass a value from form1 to another form's public sub.
The problem is that it says "it is not accesible in this context because it is 'Private'."
I've tried changing Form 1 Private Sub to Public Sub but the same error remains. How should i make it work?
Public Class Form1
Dim test(), text1 As String
Const asd = "abcabc"
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
text1 = Space(LOF(1))
test = Split(text1, asd)
HOST = test(1)
End Sub
And i want to pass HOST = test(1) value to another form
Public Class Form2
Public Sub Check()
'get the value to here
End Sub
You could pass it as a parameter:
Public Sub Check(valueToCheck as String)
'get the value to here
End Sub
Or create a property on form2 to receive it:
private _HostOrSomething As String = ""
Friend Property HostOrSomething As String
Get
Return _HostOrSomething
End Get
Set(ByVal value As String)
_HostOrSomething = value
End Set
In which case, Sub Check could use _HostOrSomething since it is local var. To use these:
HOST = Test(1)
frm2.Check(HOST)
or
HOST = Test(1)
frm2.HostOrSomething = HOST
frm2.Check
You can use global variables to pass data from one from to another
Dim A As New Integer= 10
Here how you declare the global The class can be define anywhere in the application.
Public Class GlobalVariables
Public Shared INTver As Integer
End Class
And how you use global variable to store the answer is here
GlobalVariables.INTver= A
put this lines in your "privet sub" and you can access the variable to any of your form that is in your WINDOWS application.
Related
Let's assume following example below:
When I call Form2 from Form1 and pass _name of Form1 value. When I show Form1's _name = Alex? I didn't change pname in Form2 and constructor doesn't contains ByRef.
Example code:
Public Form1
Public _name as String
Sub New
_name = "John"
Dim bla as New Form2(_name)
'now _name=Alex !!
End Sub
End Class
Public Form2
Property _name2 as String
Sub New(pname as String) 'no ByVal !!
_name2 = pname 'even if would be ByVal no pname changed !
_name2 = "Alex"
End Sub
End Class
Why is that happening?
Use Shared in variable _name:
Class Form1
Public Shared _name As String
Public Sub New()
_name = "John"
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
' Message "John"
MessageBox.Show(_name)
Dim bla As New Form2()
bla.Show()
' Message "Alex"
MessageBox.Show(_name)
End Sub
End Class
Public Class Form2
Property _name2 As String
Sub New()
_name2 = "Alex"
Form1._name = _name2
End Sub
Private Sub Form2_Load(sender As Object, e As EventArgs) Handles MyBase.Load
' message Alex
MessageBox.Show(_name2)
' message Alex
MessageBox.Show(Form1._name)
End Sub
End Class
Or
When the modifier is not entered in the signature of a constructor (method), the default is byVal. If you want to change the value of the variable in form2 you must inform byref in the form2 constructor signature:
Sub New (byref _name as String)
To change the underlying value of an argument you must use the ByRef modifer:
Specifies that an argument is passed in such a way that the called procedure can change the value of a variable underlying the argument in the calling code.
This differs slightly from ByVal:
Specifies that an argument is passed in such a way that the called procedure or property cannot change the value of a variable underlying the argument in the calling code.
By not specifying a modifier in VB.NET the compiler by default will use ByVal.
It would be good to note here that although VB.NET uses ByVal by default if not specified, VBA does not and instead by default uses ByRef. Beware of this should you ever port code from one to the other.
Furthermore you are changing name2 when instead you should be changing pname if you want to change the underlying value.
Have a look at the following code based on your example:
Public Class Form1
Private _name As String
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
_name = "John"
Dim bla As New Form2(_name)
bla.Show()
Debug.WriteLine(_name)
End Sub
End Class
Public Class Form2
Private Property _name2 As String
Public Sub New(ByRef pname As String)
InitializeComponent()
_name2 = pname
pname = "Alex"
End Sub
End Class
Before passing the value to Form2 the name is "John":
At this point I am changing the value of pname to "Alex":
Note that although I have changed the value of pname To "Alex", _name2 is still set to "John".
Notice how the value of _name changes to "Alex" because of the change made to pname:
I'm not sure what it is you're trying to achieve here but hopefully this example gives you a better understanding. The alternative way would be to use a shared variable as explained in the other answer.
I'm using a collection and structure to store some parsed data in a class, but when i try to retrieve the data it is null. On form1 i'm i can get the response string which is all the raw data. Am I adding the parsed data to the collection correctly? Did I call it on form1 correctly?
Private Sub btnStart_Click(sender As System.Object, e As System.EventArgs) Handles btnStart.Click
Dim dloader as new Downloader(blah)
'this does not work
Dim test as new _ListInfo
msgbox(test.Name) ' produces an empty message box
'this works
msgbox(dloader.Download)
End Sub
Here is my code for the class:
Public Structure _Info
Dim Name As String
End Structure
Public Class Downloader
Dim _ListCollection As New Collection(Of _ListInfo)
Public ReadOnly Property ListCollection() As Collection(Of _ListInfo)
Get
ListCollection = _ListCollection
End Get
End Property
Public Function Download() As String
'doing the download
ParseList()
Return _ResponseString
End Function
Private Sub ParseList()
_ListCollection.Clear()
Dim Name As String
Dim MyInfo As _ListInfo
MyInfo.Name = Name
_ListCollection.Add(MyInfo)
End Sub
Why do you expect it to work? You are just newing-up a structure and accessing a property. Don't you want to do something like:
Dim dloader as new Downloader(blah)
dloader.Download()
' Show first name.
MsgBox(dloader.ListCollection(0).Name)
I have a class as seen below:
Public Class parameters
Public Property test As String
Public Property test_type As String
Public Property user_test_name As String
Public Property meas As String
Public Property spec As String
...etc
End Class
I make a list of objects that I import from a csv somewhere. The user_test_name's from the list gets sent to a list box:
For Each parameters In param
' MsgBox(parameters.user_test_name)
ListBox1.Items.Add(parameters.user_test_name)
Next
now when the user selects something from the list i want the rest of the properties of that particular user_test_name object to populate in certain text/combo boxes in the application. Here is how I grab what is selected.
Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
Dim selected_name As String = ListBox1.SelectedItem()
' MsgBox(selected_name)
find_object_by_user_test_name(selected_name)
End Sub
Now i'm having difficulty finding the object with the selected_name from the list and using its properties to fill the text.combo boxes. I tried the following to no success:
Public Sub find_object_by_user_test_name(ByVal description)
MsgBox(description)
Dim matches = From parameters In param
Where parameters.user_test_name = description
Select parameters
' MsgBox(matches)
' MsgBox(matches.user_test_name)
TextBox1.Text = matches.test
TextBox2.Text = matches.test_name
etc,,, on and on
' populate_area(matches)
End Sub
Instead of adding the name (a string) to the ListBox, add your actual INSTANCE to it.
First, override ToString() in your class so that it displays properly in your ListBox:
Public Class parameters
Public Property test As String
Public Property test_type As String
Public Property user_test_name As String
Public Property meas As String
Public Property spec As String
Public Overrides Function ToString() As String
Return user_test_name
End Function
End Class
Next, add each instance to the ListBox:
For Each parameters In param
ListBox1.Items.Add(parameters)
Next
Now, the SelectedIndexChanged() event, you can cast the SelectedItem() item back to parameters and you already have everything at your disposal:
Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
If ListBox1.SelectedIndex <> -1 Then
Dim P As parameters = DirectCast(ListBox1.SelectedItem, parameters)
' ... do something with "P" ...
Debug.Print(P.user_test_name & " --> " & P.test)
End If
End Sub
If the user_test_names are unique, it may be easier to use a dictionary and retrieve the objects that way.
Dim params As New Dictionary(Of String, parameters)
params.add(MyParameterObject.user_test_name, MyParameterObject)
Then
Private Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged
Dim selected_name As String = ListBox1.SelectedItem()
Dim selected_param as parameters = params(selected_name)
End Sub
Something like this should do it:
Public Sub find_object_by_user_test_name(ByVal description As String)
' assuming param is your list of parameter objects
For Each p In param
If p.user_test_name = description Then
TextBox1.Text = p.test
TestBox2.Text = p.test_name
...
Exit For
End If
Next
End Sub
A few notes about your code. First, you can't allow two objects to have the same user_test_name. Second, you can't use parameters as a variable name if you already have a class called parameters in your current namespace (which you do).
There is a simpler solution than any of these--just do the following:
Dim i as Integer = ListBox1.SelectedIndex
Then you can use i as an index to your original list of objects.
I have a subsidiary form where I can enter data and then save it before closing the form and going back to using the main form.
When I re-open the subsidiary form, I cannot see the changes in the data that I had entered earlier.
Can anyone tell me where I'm wrong ?
MainForm.vb
Public Class Maincls
oTestObj as New Testcls
oTestObj.XYZ = "XYZ"
Private Sub SoftwareSettingsToolStripMenuItem_Click(sender As System.Object, e As System.EventArgs) Handles SoftwareSettingsToolStripMenuItem.Click
Testcls.tbXYZ.Text = oTestObj.m_XYZ
Testcls.Show()
End Sub
End Class
Form_Testcls.vb
Public Class Testcls
Structure Params
Dim m_XYZ as String
End Structure
Dim oParams as Params
Public Sub New ()
InitializeComponent()
End Sub
Private Sub btnOK_Click(sender As System.Object, e As System.EventArgs) Handles btnOK.Click
XYZ = tbXYZ.Text
Me.Hide()
End Sub
Public Property XYZ() As String
Get
Return Me.oparams.m_XYZ
End Get
Set(ByVal value As String)
Me.oparams.m_XYZ = value
End Set
End Property
End Class
I think in windows forms the work around for this is to create a static class and add properties according to your requirement. Then populate these static properties on closing of your form. Now you can use the value set in the static data members, unless otherwise you change them on any other event.
Edit: In vb.net the Static is actually NonInheritable
can we have a single global variable which can be manipulated by multiple forms
In short, yes. You can have a global variable in a module (.mod) file or a class (.vb) file.
Module Module2
Public variable As String = "Testing"
End Module
Declare a variable like this:
Public Shared myVariable as Type
and access it from any form.
You can access a single variable from any form, if it is declared as public.
If you are defining it in form1 and want to use it in form2, then from inside form2 you can call the variable as - form1.<variable_name>
Take an example-
Form1 code
Public Class Form1
Public a As Integer = 10
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Form2.Show()
End Sub
End Class
Form 2 code
Public Class Form2
Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
MsgBox(Form1.a)
End Sub
End Class
Yes, it can be done. If you declare it as shared it will exist in only one instance.
Public Class SomeClass
Public Shared SomeField As String
End Class
I would, however, recommend to wrap access to the field into a property:
Public Class SomeClass
Private Shared _someValue As String
Public Shared Property SomeProperty() As String
Get
Return _someValue
End Get
Set(ByVal value As String)
_someValue = value
End Set
End Property
End Class
By wrapping it into a property you will make it easier to troubleshoot problems around the value in case such scenarios would appear in the future.
What you are looking for is the "singleton pattern".
But first, you should ask yourself if you really need it. Maybe this variable could be passe as a parameter to a function or a property.
Use
Public x As Integer
On any Of the Forms and then when you want to use that variable on other form then you can type the form name and then a dot and then the variable name
like this
form1.x
Cheers!!!