[RESOLVED] [2005] How to avoid opening duplicate MDI child form ?

[LuxCoder]

How do i avoid opening duplicate MDI child form which is already open. I am using the following codes for opening MDI child form:

Private Sub EmployeeToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles EmployeeToolStripMenuItem.Click
        Dim childform As New Employee
        childform.MdiParent = Me
        childform.Show()
    End Sub

What changes should be made ?

[jmcilhinney]

I would suggest implementing the Singlton patter, so the form itself will prevent any more than one instance being created. There are numerous examples already posted.

[LuxCoder]

Where do i find the Singlton patter and how do i implement it, Sir ?

[jmcilhinney]

Sorry for my poor typing. It's the Singleton pattern you want. Search the forum and you'll find the aforementioned examples.

[LuxCoder]

I have used the following code for Singleton... I cant figure out the problem.

Public Class SingletonForm
        Private Shared newcust As SingletonForm
 
        Public Shared ReadOnly Property Instance() As SingletonForm
            Get
                If newcust Is Nothing OrElse newcust.IsDisposed Then
                    newcust = New SingletonForm
                End If
                Return newcust
            End Get
        End Property
 
        Private Sub New()
 
            InitializeComponent()
 
        End Sub
    End Class
 
    Private Sub NewToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles NewToolStripMenuItem.Click
 
 
        SingletonForm.Instance.MdiParent = Me
        SingletonForm.Instance.Show()
        SingletonForm.Instance.Activate()     
 
        'Dim childform As New newCust 
        'childform.MdiParent = Me   
        'childform.Show()
 
    End Sub

[xoggoth]

Bit new to all this so I probably do things a wierd way but what I do is set global pointer to form class:-

Public frmInfo As cfrmInfo

Open form like this:-

If frmInfo Is Nothing Then
Dim info As New cfrmInfo : frmInfo = info
End If

And stick a frmInfo = nothing in the form closed event.

[jmcilhinney]

I have used the following code for Singleton... I cant figure out the problem.[/HIGHLIGHT]

You imply that there's a problem yet you don't give any information about it. Are you saying that that doesn't prevent more than one instance? Please be clear about what the issues are. Feel free to post more than one line in explanation.

[LuxCoder]

Sir, please help... my form name is newcust to which i want to apply singleton pattern. what changes should be made to my code in the first post ?

[jmcilhinney]

If you ask for help and someone who is trying to help you asks a question, I suggest that you answer it. Chances are that they asked the question because they need more infromation in order to help you. I aksed you a question in my previous post.

[nUflAvOrS]

This is my suggest solution

Public Sub ChildFormLoading(ByVal ChildForm As Form, ByVal FormName As String)
        For Each f As Form In Me.MdiChildren ' Loop all childform

            If Not f.Name = FormName Then 
                f.close() 'Close others form

            End If
        Next
        For Each f As Form In Me.MdiChildren  ' Scan all childform

            If f.Name = FormName Then 'if Same Name then exit sub function
                Exit Sub

            End If
        Next
        ChildForm.MdiParent = Me
        ChildForm.Show()
    End Sub

[LuxCoder]

Thanks nuflavors, but that is not what i exactly want. I want to check while opening a form, if that form is already open or not. If it is open then it should activate and if it is not then a new form in opened. i have tried the MDIwindowlist method where my code goes like this :

Dim childform As newCust
        If MenuStrip1.MdiWindowListItem.IsMdiWindowListEntry.Equals(newCust) = True Then
            newCust.Activate()
        Else
            childform = New newCust
            childform.MdiParent = Me
            childform.Show()
        End If

Here i want to check whether the MDIWindowList has newcust in it ? If it has then the already opened form (newcust) gets activated otherwise a new form (newcust) is opened. But i dont know whats wrong with my code... it's still opening the form (newcust) as many times i am clicking.

I want to apply the singleton form pattern here (as suggested by Mr. JMC) but i do not know why my code is not working.

[jmcilhinney]

The code in post #5 works as it's supposed and apparently you are determined not to answer my question. In that case I can't help you. If I have to post three times just to get some information then it just isn't worth it.

[LuxCoder]

I am using the following code to prevent opening duplicate MDIchildform - Customer (which is working fine) but it doesn't bring the already opened MDIchildform - Customer, in case it is underlying behind some other MDIchildform.

Private Sub NewToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles NewToolStripMenuItem.Click
        Customer.MdiParent = Me
        If Customer IsNot Nothing Then
            Customer.Show()
        ElseIf Customer IsNot ActiveMdiChild Then
            Customer.BringToFront()
        End If
    End Sub

Please suggest what's wrong.

[bmahler]

i use this function to load mdi children

    Private Sub LoadMdiChild(ByVal f As Form)
        If Me.MdiChildren.Length > 0 Then
            For i As Integer = 0 To Me.MdiChildren.Length - 1
                If Me.MdiChildren(i).Name = f.Name Then
                    Me.MdiChildren(i).BringToFront()
                    f.Dispose()
                    Exit Sub
                End If
            Next
            f.MdiParent = Me
            f.Show()
        Else
            f.MdiParent = Me
            f.Show()
        End If
    End Sub

To call it I simply call

LoadMdiChild(New AdminForm)

[onlyGirl]

Private Sub EmployeeToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles EmployeeToolStripMenuItem.Click
Dim childform As New Employee
childform.MdiParent = Me
childform.Show()
End Sub

Just do this, let's say it's your frmEmployee

frmEmployee.Show()
frmEmployee.Focus()
frmEmployee.MdiParent = Me

[LuxCoder]

Thanks.. That worked great!

[shakti5385]

Thanks.. That worked great!

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