[RESOLVED] Form sharing problem

[Cyber-Drugs]

Form2 is not passing over information to Form1...

Code for Form2:

Private m_myVar As String
 
Public Property listItem() As String
  Get
    Return Me.m_myVar
  End Get
  Set(ByVal Value As String)
    Me.m_myVar = Value
  End Set
End Property
 
Private Sub Button1_Click(ByVal sender as System.Object, ByVal e As System.EventArgs)  Handles Button1.Click
  Dim lv As ListViewItem = ListView1.SelectedItems(0)
  Me.m_myVar = lv.SubItems(2).Text
  Me.listItem = lv.SubItems(2).Text
  Me.Close
End Sub

And for Form1 I have this:

Dim myForm As New Form2
myForm.ShowDialogue()
MessageBox.Show(myForm.listItem)

on Form2 I get the correct text.
on Form1 (which is loaded after Form2), I get a blank field.

Any ideas?

Cheers.

[Shaggy Hiker]

Well, I may be misunderstanding, but the snippet of code you have labeled Form1 will create a NEW instance of Form2, and get the info from that.

You state that form2 is loaded before form1, which I interpret to mean that there is an existing instance of Form2 at the time the code on Form1 is run. If you are expecting the code you listed to use the already existing instance of Form2, it is not. Instead, it is using myForm, which is a local instance of Form2 created in the line above the MessageBox line.

To use the existing Form2, you will have to reference that instance. I don't know how you have it declared, so it may or may not be in scope for the instance of Form1 that you have.

Keep in mind that a form is just like any other variable (ok, that's not true, but it is true for this example). Think of it as an integer. If you declared one instance in a module, and declared another instance in a sub on a form, you would not expect that second instance to take on the value of the first instance. The same thing is happening here.

[Cyber-Drugs]

OK, so how do I call the information form Form2 into Form1? Is there a way of submitting the information or making a variable that can be read in any of the Forms in this project like Session Variables?

Cheers.

[Shaggy Hiker]

The form itself could be made as a session variable. After all, you must have declared that original form2 somewhere with a statement like:

Dim mForm as New Form2.

If that was done in a sub or function, then only that sub or function would be able to see mForm, however, if you were to put it outside the sub or function:

Public mForm as New Form2

Then it becomes a global instance of Form2, and is visible to all other variables in the application, including Form1. If you do that, you would simply need to get rid of the duplicate declaration that you have in Form1 (ok, I also have a slightly different name, but you get the idea), and it should work the way you want.

Of course, then you have this global Form2 kicking around that you have to manage. That may be no big deal, or it may be that you will want to explicitly dispose of it at some time, or something like that. There are other, more complicated, ways of doing this if you want to encapsulate things more, but this is the easiest way, and one I use often when I have a form that other forms and functions need access to.

[Cyber-Drugs]

OK, Im still having some troubles...

Is someone willing to give me a hand over instant messenger, and then I can post the result once one is found?

Cheers.

[Cyber-Drugs]

Anybody?

[mar_zim]

if you want to get the value of the property in form2 then make the property as public shared.
like this one

'in your form2
Shared s As String
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        mystring() = TextBox1.Text
        Dim f As New Form1()
        f.ShowDialog()
    End Sub
 
    Public Shared Property mystring() As String
        Get
            Return s
        End Get
        Set(ByVal Value As String)
            s = Value
        End Set
    End Property
'in form1
'no need to instantiate the form2
 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        MessageBox.Show(Form2.mystring())
    End Sub

edit: no need to put public in shared property because in vb.net shared methodd by default is public where as in c# static methods cannot be accessed outside of the class if it's not declared public.

[Cyber-Drugs]

Sorry for the confusing, let me explain a bit better...


Form1 loads up
Form1 shows Form2 with ShowDialogue()
Form2 gets some information stored into a Public Property within Form2
Form2 Closes
Form1 tries to access Form2's Public Property but gets a blank

How would I work around that?

[mar_zim]

ok if that is the case then no need to instantiate your form2 twice
instatiate your form2 once and declared it globally
just like this one

'in your form1
Dim f As New Form2()
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
 
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        f.ShowDialog()
        MessageBox.Show(f.mystring)
    End Sub
 
'in your form2
Dim s As String
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        mystring() = TextBox1.Text
    End Sub
 
    Public Property mystring() As String
        Get
            Return s
        End Get
        Set(ByVal Value As String)
            s = Value
        End Set
    End Property

[Cyber-Drugs]

OK, a friend of mine helped me fix this, basically on Form1 I had to change the code to this:

Dim csvFile As String
Dim Form2 As New Form2
If Form2.ShowDialog() = DialogResult.OK Then
  csvFile = Form2.listItem
End If

and on Form2 I needed to add

Me.DialogResult = DialogResult.OK

just before closing the Form.


wooooooooooo.