Textbox update from other form

Here is 3 forms, form3, form1, form2.
form1 has textbox.
A. Start form3, form3 load form1, form1 load form2 and form2 try updating form1.textbox but failed.
B. But start form1, form1 load form2 and form2 try updating form1.textbox and then textbox is normally updated.

I don't know why B succeed but A fail.
How do I do to succeed in A?
(I attached project to show this.)

I havent looked at your project but you can't load something from something that has not been created yet until you load form1 with the textbox it doesnt exist

So if i understand correctly in scenario A you are trying to load form 3 first, then form2 and have form2 get information form form1 textbox?

You have to load form 1 first

perhaps a more senior programmer will correct me or offer a better idea but i beleive that is your problem

Why do you want to load something from a textbox that hasnt been created yet. in theory the user wouldnt have put any information in the textbox yet, so you must have a default value in the textbox, why not just use that value when you load form2?

Because you are creating new instances(as you should using New keyword)

Code:

---

Dim frm As New Form1 frm.ShowDialog()

---

then trying to update the default instance of form1

Code:

---

        Form1.TextBox1.Text = "AAAA"

---

Read Johns excellent tutorial on http://jmcilhinney.blogspot.co.uk/ Managing Data Among Multiple Forms (Part 2)

How ever it should be noted as mentioned it's a lazy approach. The controls Modifier should be private. If access is needed we should handle this correctly.

Your form that updates the textbox should look a little some thing like

TextBox is private not friend.

vb Code:

Public Class MainForm
 
    Public WriteOnly Property UpdateDisplayValue As String
        Set(ByVal value As String)
            If value.Trim <> String.Empty Then
                Me.PrivateTextBox.Text = value
            End If
        End Set
    End Property
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim frm As New UpdateForm(Me)
        frm.ShowDialog()
    End Sub
 
End Class

The form that updates the textbox looks a little some thing like

vb Code:

Public Class UpdateForm
 
    Private m_mainForm As MainForm
 
    Public Sub New(ByVal MainForm As MainForm)
        InitializeComponent()
        Me.m_mainForm = MainForm
    End Sub
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Me.Close()
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Me.m_mainForm.UpdateDisplayValue = "Some value"
    End Sub
End Class

All exe removed

http://www.freefilehosting.net/windowsapplication1