singleton class help needed (repost from vsnet.general posted the

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  • Start date Start date
G

Guest

Please help this is driving me nuts. I have 2 forms, 1 user class and I am
trying to implement a singleton class. Form 1 should create a user object
and populate some properties in user. Form2 should then have access to those
user properties. I am not getting the property value from user that was set
in form1.

Sorry for posting so much code but I need help bad. How do i make this work?

Thanks
Mike


'Form1.vb
'--------------------
Public Class Form1
Inherits System.Windows.Forms.Form
Dim m_User As New User
Public Property MyUser() As User
Get
Return m_User
End Get
Set(ByVal value As User)
m_User = value
End Set
End Property

#Region " Windows Form Designer generated code "

Public Sub New()
MyBase.New()

'This call is required by the Windows Form Designer.
InitializeComponent()

'Add any initialization after the InitializeComponent() call

End Sub

'Form overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub

'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer

'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
Friend WithEvents Button1 As System.Windows.Forms.Button
Friend WithEvents TextBox1 As System.Windows.Forms.TextBox
<System.Diagnostics.DebuggerStepThrough()> Private Sub
InitializeComponent()
Me.Button1 = New System.Windows.Forms.Button
Me.TextBox1 = New System.Windows.Forms.TextBox
Me.SuspendLayout()
'
'Button1
'
Me.Button1.Location = New System.Drawing.Point(88, 136)
Me.Button1.Name = "Button1"
Me.Button1.Size = New System.Drawing.Size(120, 32)
Me.Button1.TabIndex = 0
Me.Button1.Text = "Button1"
'
'TextBox1
'
Me.TextBox1.Location = New System.Drawing.Point(64, 56)
Me.TextBox1.Name = "TextBox1"
Me.TextBox1.Size = New System.Drawing.Size(168, 20)
Me.TextBox1.TabIndex = 1
Me.TextBox1.Text = "TextBox1"
'
'Form1
'
Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
Me.ClientSize = New System.Drawing.Size(292, 273)
Me.Controls.Add(Me.TextBox1)
Me.Controls.Add(Me.Button1)
Me.Name = "Form1"
Me.Text = "Form1"
Me.ResumeLayout(False)

End Sub

#End Region

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

MyUser.login = Me.TextBox1.Text.ToString

Dim Form2 As New Form2
Form2.ShowDialog()
End Sub
End Class

'Form2.vb
'------------------------

Public Class Form2
Inherits System.Windows.Forms.Form


#Region " Windows Form Designer generated code "

Public Sub New()
MyBase.New()

'This call is required by the Windows Form Designer.
InitializeComponent()

'Add any initialization after the InitializeComponent() call

End Sub

'Form overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Dispose()
End If
End If
MyBase.Dispose(disposing)
End Sub

'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer

'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
Friend WithEvents frm2textbox As System.Windows.Forms.TextBox
Friend WithEvents Button1 As System.Windows.Forms.Button
<System.Diagnostics.DebuggerStepThrough()> Private Sub
InitializeComponent()
Me.frm2textbox = New System.Windows.Forms.TextBox
Me.Button1 = New System.Windows.Forms.Button
Me.SuspendLayout()
'
'frm2textbox
'
Me.frm2textbox.Location = New System.Drawing.Point(64, 80)
Me.frm2textbox.Name = "frm2textbox"
Me.frm2textbox.Size = New System.Drawing.Size(168, 20)
Me.frm2textbox.TabIndex = 0
Me.frm2textbox.Text = "TextBox1"
'
'Button1
'
Me.Button1.Location = New System.Drawing.Point(88, 152)
Me.Button1.Name = "Button1"
Me.Button1.Size = New System.Drawing.Size(112, 32)
Me.Button1.TabIndex = 1
Me.Button1.Text = "Button1"
'
'Form2
'
Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
Me.ClientSize = New System.Drawing.Size(292, 273)
Me.Controls.Add(Me.Button1)
Me.Controls.Add(Me.frm2textbox)
Me.Name = "Form2"
Me.Text = "Form2"
Me.ResumeLayout(False)

End Sub

#End Region






Private Sub Form2_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
Dim ThisUser As User = MySingletonClass.MyForm1.MyUser
MessageBox.Show(ThisUser.login)
End Sub
End Class

'user.vb
'----------------------------
Public Class User
'private fields exposed as properties
Private _login As String

Public Property login() As String
Get
Return _login
End Get
Set(ByVal Value As String)
_login = Value
End Set
End Property
End Class

'MySingleton.vb
'------------------------

Public Class MySingletonClass
Private Shared m_Form1 As Form1
Public Shared Function MyForm1()
If IsNothing(m_Form1) Then
m_Form1 = New Form1
Return m_Form1
Else
Return m_Form1
End If
End Function
End Class
Was this post helpful to
 
Hi
Looks like you are getting messy somewhere.In form1 you are creating
object of User class which is not shared. In form2 you are trying to
access MySingletonClass which is definetly shared but the user objects
are different.

I think just make the user class property shared everything will be
fine. If you want solve it by this way then

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click


MyUser1.login = Me.TextBox1.Text.ToString
// Add this
MySingletonClass.MyForm1.MyUse­r = Myuser1

Dim Form2 As New Form2
Form2.ShowDialog()
End Sub
End Class

Shivprasad Koirala
C# , VB.NET , SQL SERVER , ASP.NET Interview Questions
http://www.geocities.com/dotnetinterviews/
 
The singleton is supposed to contain the object that you want to share.
Your singleton contains Form1. Is Form1 the object you want to share? I
thought that User was the object you wanted to share.

So, to fix the singleton, have it manage the creation of User objects. You
will need to remove any uses of "new User" from any other class (including
Form1, where it occurs about four lines in).

On the other hand, if you just want to pass a value to Form2, a singleton is
a nutty idea.
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click

MyUser.login = Me.TextBox1.Text.ToString

Dim Form2 As New Form2
Click to expand...
Form2.SetMyLogin(Me.TextBox1.Text) ' <-- add this line...
and add a method to Form2 to get this value.
Form2.ShowDialog() ' <-- now,
in Form_Load for Form2, put the value into the display
End Sub
Click to expand...


HTH,
--
--- Nick Malik [Microsoft]
MCSD, CFPS, Certified Scrummaster
http://blogs.msdn.com/nickmalik

Disclaimer: Opinions expressed in this forum are my own, and not
representative of my employer.
I do not answer questions on behalf of my employer. I'm just a
programmer helping programmers.
--
 
Singleton pattern (in C#):

public class MySingleton
{
private static MySingleton m_Singleton = null;
static MySingleton() { m_Singleton = new MySingleton(); }
private MySingleton() { /* initialisation code */ }
public static MySingleton Singleton
{
get
{
if(m_Singleton == null) { m_Singleton = new MySingleton(); }
return(m_Singleton);
}
}
}

Use this from code :

MySingleton ms = MySingleton.Singleton;
 
billr said:
Singleton pattern (in C#):

public class MySingleton
{
private static MySingleton m_Singleton = null;
static MySingleton() { m_Singleton = new MySingleton(); }
private MySingleton() { /* initialisation code */ }
public static MySingleton Singleton
{
get
{
if(m_Singleton == null) { m_Singleton = new MySingleton(); }
return(m_Singleton);
}
}
}

Use this from code :

MySingleton ms = MySingleton.Singleton;
Click to expand...

That's a rather long-winded way of doing it - why bother with the
nullity check in the property when you've got a static constructor?

You might also consider moving the contents of the static constructor
to the declaration (depending on how lazy you want the initialization
to be) and perhaps even making it a public static readonly field.
 
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