Visual Basic

20-Jul-05 7:41

i have two forms:
--------------
Public Class Form1
Inherits System.Windows.Forms.Form

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim fr As Form2
fr.test()
End Sub
End Class

---------------
Public Class Form2
Inherits System.Windows.Forms.Form

Sub test()
MsgBox("Hello")
End Sub
End Class
---------------
with this i have the error:
"An unhandled exception of type 'System.NullReferenceException' occurred in WindowsApplication3.exe

Additional information: Object reference not set to an instance of an object."

My question is: how i can acess from form1 to a sub or a function in form2. Putting "shared sub" it works but exists another way to make this?

waiting you help.

Thanks.

Anonymous20-Jul-05 8:55

20-Jul-05 8:55

Here's a good article:

http://www.devcity.net/Articles/94/multipleforms.aspx[^]

Anonymous20-Jul-05 9:16

20-Jul-05 9:16

makeko wrote:
Public Class Form1
Inherits System.Windows.Forms.Form

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim fr As Form2
fr.test()
End Sub
End Class

"An unhandled exception of type 'System.NullReferenceException' occurred in WindowsApplication3.exe

Additional information: Object reference not set to an instance of an object."

Your error occurs at fr.test() because you haven't created an instance of Form2. Change the line:
Dim fr As Form2
TO
Dim fr As New Form2

Now you should be able to access fr.test()

makeko21-Jul-05 4:36

21-Jul-05 4:36

It works. But if form2 already exists and i want to put data on it.

Like this:

-----------------------------

Public Class Form1<br />
    Inherits System.Windows.Forms.Form<br />
<br />
    Public Sub teste()<br />
        TextBox1.Text = "Hello"<br />
    End Sub<br />
<br />
    Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click<br />
        Dim fr2 As New Form2<br />
        fr2.Show()<br />
    End Sub<br />
End Class

------------------------------

Public Class Form2<br />
    Inherits System.Windows.Forms.Form<br />
<br />
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click<br />
        Dim fr1 As Form1<br />
        fr1.teste()  ***<br />
    End Sub<br />
End Class

------------------------------

*** ERROR: "An unhandled exception of type 'System.NullReferenceException' occurred in WindowsApplication3.exe

Additional information: Object reference not set to an instance of an object."

Without using "shared sub", i don't know how to put this working.
Waiting help...

Thanks.

Anonymous21-Jul-05 5:20

21-Jul-05 5:20

makeko wrote:
Public Class Form2
Inherits System.Windows.Forms.Form

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim fr1 As Form1
fr1.teste() ***
End Sub
End Class

------------------------------

*** ERROR: "An unhandled exception of type 'System.NullReferenceException' occurred in WindowsApplication3.exe

Additional information: Object reference not set to an instance of an object."

You made the same error...but this time you did not create an instance of Form1 in the Form2 button event.

You had:

Dim fr1 As Form1<br />
fr1.teste() ***

Where you should have

Dim fr1 As New Form1<br />
fr1.teste() ***

Also, please take the time to read this article, it may help you with your situation.
http://www.devcity.net/Articles/94/multipleforms.aspx[^]

makeko21-Jul-05 8:08

21-Jul-05 8:08

Ok, that work but with that the text on the textbox isn't modified, because is created a new instance and i have already one Form1 created and i want to change the text on texbox of this one.

If you can, try the code that I put here previously.

thanks for the help...

Anonymous21-Jul-05 9:00

21-Jul-05 9:00

The reason why the textbox isn't modified, as you have said already, is because you are creating new instances of Form1 or Form2 in every button event. Is Form1 acting as a dialog box? If so, have you tried the InputBox class??

If you are trying to access a sub procedure inside a Form, you may want to consider using Events or as you have said before, a Shared method. But it really depends on what this "method" is trying to accomplish.

makeko22-Jul-05 7:01

22-Jul-05 7:01

What i'm trying is:

I have 1 form ( form1 ) that when i click in a button open another form ( form2 ) with a datagrid where i can select one user with a keypress or a doubleclick. After that, the form2 closes automatically and i want that the data in the row selected on datagrid goes to textboxs in form1. I have the data in one dataset.

How you would decide this problem?
Can you tell me the better way to do that?

thanks for the help.

Anonymous22-Jul-05 10:38

22-Jul-05 10:38

I would suggest using Events to perform what you would like to do. I posted a link earlier, but I'm assuming you haven't read it.

http://www.devcity.net/Articles/94/multipleforms.aspx[^]

Anyway, since you are not willing to read the link...here is some sample code:

In Form2 (the one with a Datagrid):

<br />
Public Class Form2<br />
    Inherits System.Windows.Forms.Form<br />
<br />
#Region " Windows Form Designer generated code "<br />
...<br />
#End Region<br />
<br />
'declare an event that can be caught in Form1 code<br />
'you can name this whatever you want<br />
    Public Event OnRowDoubleClicked()<br />
<br />
    Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load<br />
        'databind your datagrid here or in design mode<br />
    End Sub<br />
<br />
    Private Sub DataGrid1_DoubleClick(ByVal sender As Object, ByVal e As System.EventArgs) Handles DataGrid1.DoubleClick<br />
'This is if you want to close your window on a when <br />
'the user double clicks a row<br />
<br />
'raise the event to be caught in Form1<br />
        RaiseEvent OnRowDoubleClicked()<br />
<br />
        Me.Close()<br />
    End Sub<br />
<br />
    Private Sub Form2_Closing(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) _<br />
        Handles MyBase.Closing<br />
        'cancel closing of form<br />
        e.Cancel = True<br />
        'hide the form from the user<br />
        Me.Hide()<br />
    End Sub<br />
End Class<br />

Now in Form1 (the one with the Button and TextBox):

<br />
Public Class Form1<br />
    Inherits System.Windows.Forms.Form<br />
<br />
#Region " Windows Form Designer generated code "<br />
...<br />
#End Region<br />
<br />
'declare a Form2 with events - the key to handling the <br />
'doubleclick in Form2<br />
    Private WithEvents f2 As Form2<br />
<br />
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click<br />
'display the form to the user<br />
<br />
'check if Form2 has been created<br />
        If Not f2 Is Nothing Then<br />
            If Not f2.IsDisposed Then<br />
'display form if not disposed<br />
                f2.ShowDialog()<br />
            Else<br />
'create new instance of Form2<br />
                f2 = New Form2<br />
                f2.ShowDialog()<br />
            End If<br />
        Else<br />
'create new instance of Form2<br />
            f2 = New Form2<br />
            f2.ShowDialog()<br />
        End If<br />
<br />
    End Sub<br />
<br />
<br />
    Private Sub f2_OnRowDoubleClicked() Handles f2.OnRowDoubleClicked<br />
        'handle the double click event in the datagrid of Form2<br />
'now you can access the Datagrid information since it is a public control <br />
'in Form2...like so:<br />
TextBox1.Text = f2.DataGrid1....<br />
    End Sub<br />
End Class<br />

It's up to you to figure out the rest...but I really do suggest you read the article that I linked! D'Oh! | :doh:

A.S.

makeko26-Jul-05 7:36