Telling if you have open Children?

Troy

Troy

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Is there a way to tell programmatically if you have any open MDI children windows?

I need to be able to enable some buttons only if there are open MDI Children.
 
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Form.ActiveMdiChild property:
Returns a Form that represents the currently active MDI child window, or a null reference (Nothing in Visual Basic) if there are currently no child windows present.
Click to expand...
If you need to know when this changes you can use the Form.MdiChildActivate event.
Occurs when a multiple-document interface (MDI) child form is activated or closed within an MDI application.
Click to expand...
 
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ok I've tried this the problem is when I close the form the ActiveMDIChild still acts as if there is an active child and isn't a null.

VB.NET: 
[SIZE=2][COLOR=#0000ff]Private[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] frmMain_MdiChildActivate([/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] sender [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Object[/COLOR][/SIZE][SIZE=2], [/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] e [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.EventArgs) [/SIZE][SIZE=2][COLOR=#0000ff]Handles[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Me[/COLOR][/SIZE][SIZE=2].MdiChildActivate[/SIZE]
 
[SIZE=2][COLOR=#0000ff]If[/COLOR][/SIZE][SIZE=2] ([/SIZE][SIZE=2][COLOR=#0000ff]Not[/COLOR][/SIZE][SIZE=2] IsDBNull(sender)) [/SIZE][SIZE=2][COLOR=#0000ff]Then[/COLOR][/SIZE]
[SIZE=2]     mnuWindowTileH.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]True[/COLOR][/SIZE]
[SIZE=2]     mnuWindowTileV.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]True[/COLOR][/SIZE]
[SIZE=2]     mnuWindowCascade.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]True[/COLOR][/SIZE]
[SIZE=2]     mnuWindowArrangeIcons.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]True[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]Else[/COLOR][/SIZE]
[SIZE=2]     mnuWindowTileH.Enabled = F[/SIZE][SIZE=2][COLOR=#0000ff]alse[/COLOR][/SIZE]
[SIZE=2]     mnuWindowTileV.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]False[/COLOR][/SIZE]
[SIZE=2]     mnuWindowCascade.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]False[/COLOR][/SIZE]
[SIZE=2]     mnuWindowArrangeIcons.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]False[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]If[/COLOR][/SIZE]
 
[SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE]
 
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The 'sender' in events is the object that raised the event, for form events they are always the form instance (returns same instance as Me keyword in the class).
You didn't check Form.ActiveMdiChild property as I can see.
Also, what is that IsDBNull? DbNull is not the same as Nothing.
 
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:confused: John, When I try Form.ActiveMDIChild all I get for an option on Form is Form.ActiveForm?


addendum:

I tried again and wrote this:

VB.NET: 
[SIZE=2][COLOR=#0000ff]Private[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] frmMain_MdiChildActivate([/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] sender [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Object[/COLOR][/SIZE][SIZE=2], [/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] e [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.EventArgs) [/SIZE][SIZE=2][COLOR=#0000ff]Handles[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Me[/COLOR][/SIZE][SIZE=2].MdiChildActivate[/SIZE]
[SIZE=2][COLOR=#0000ff]If[/COLOR][/SIZE][SIZE=2] frmBrowser.ActiveMdiChild [/SIZE][SIZE=2][COLOR=#0000ff]Is [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Nothing [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Then[/COLOR][/SIZE]
[SIZE=2]    mnuWindowTileH.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]False[/COLOR][/SIZE]
[SIZE=2]    mnuWindowTileV.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]False[/COLOR][/SIZE]
[SIZE=2]    mnuWindowCascade.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]False[/COLOR][/SIZE]
[SIZE=2]    mnuWindowArrangeIcons.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]False[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]Else[/COLOR][/SIZE]
[SIZE=2]    mnuWindowTileH.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]True[/COLOR][/SIZE]
[SIZE=2]    mnuWindowTileV.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]True[/COLOR][/SIZE]
[SIZE=2]    mnuWindowCascade.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]True[/COLOR][/SIZE]
[SIZE=2]    mnuWindowArrangeIcons.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]True[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]If[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE]

But it acts like it's nothing and goes through to the else then exits.

It says it's nothing after I open a child and close a child. I step through in debug to see it walk through the lines
 
Last edited:
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Maybe you didn't try with an actual form instance? The Form template class doesn't have any mdi children by default, but your form does.
 
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ROFLMAO .... I feel so stupid I got it !
 
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VB.NET: 
[SIZE=2][COLOR=#0000ff]Private[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] frmMain_MdiChildActivate([/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] sender [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Object[/COLOR][/SIZE][SIZE=2], [/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] e [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.EventArgs) [/SIZE][SIZE=2][COLOR=#0000ff]Handles[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Me[/COLOR][/SIZE][SIZE=2].MdiChildActivate[/SIZE]
 
[SIZE=2][COLOR=#0000ff]If [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Me[/COLOR][/SIZE][SIZE=2].ActiveMdiChild [/SIZE][SIZE=2][COLOR=#0000ff]Is [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Nothing [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Then[/COLOR][/SIZE]
[SIZE=2]     mnuWindowTileH.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]False[/COLOR][/SIZE]
[SIZE=2]     mnuWindowTileV.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]False[/COLOR][/SIZE]
[SIZE=2]     mnuWindowCascade.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]False[/COLOR][/SIZE]
[SIZE=2]     mnuWindowArrangeIcons.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]False[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]Else[/COLOR][/SIZE]
[SIZE=2]     mnuWindowTileH.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]True[/COLOR][/SIZE]
[SIZE=2]     mnuWindowTileV.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]True[/COLOR][/SIZE]
[SIZE=2]     mnuWindowCascade.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]True[/COLOR][/SIZE]
[SIZE=2]     mnuWindowArrangeIcons.Enabled = [/SIZE][SIZE=2][COLOR=#0000ff]True[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]If[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]End[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE]
lol my code now.

I wasn't comprehending what your were telling me correctly, Now I understand what you were saying ... Uh Duh!
 
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Excellent, that was around what I was thinking, does it work also?
 
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:D Yes this works exactly as I want allowing me to add more controls that I only want enabled while there are active children.
 
Last edited:
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Next question though lol is there a way to count the number of active child forms? or perhaps a property already setup that does that?
 
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Me.MdiChildren.Length
 
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lol jeese , I wish I knew Why I'm having so much trouble

VB.NET: 
[SIZE=2][COLOR=#0000ff]Private [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] mnuWindowCloseAllOpenRecords_Click([/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] sender [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.Object, [/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] e [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.EventArgs) [/SIZE][SIZE=2][COLOR=#0000ff]Handles[/COLOR][/SIZE][SIZE=2] mnuWindowCloseAllOpenRecords.Click[/SIZE]
[SIZE=2][COLOR=#0000ff]Dim[/COLOR][/SIZE][SIZE=2] indx [/SIZE][SIZE=2][COLOR=#0000ff]As [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Integer[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]For[/COLOR][/SIZE][SIZE=2] indx = 0 [/SIZE][SIZE=2][COLOR=#0000ff]To [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Me[/COLOR][/SIZE][SIZE=2].MdiChildren.Length - 1[/SIZE]
[SIZE=2][COLOR=#0000ff]    Me[/COLOR][/SIZE][SIZE=2].MdiChildren(indx).Close()[/SIZE]
[SIZE=2][COLOR=#0000ff]Next[/COLOR][/SIZE]

I get an Index out of Range error.
 
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ok nm got it!

VB.NET: 
[SIZE=2][COLOR=#0000ff]Private [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] mnuWindowCloseAllOpenRecords_Click([/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] sender [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.Object, [/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] e [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.EventArgs) [/SIZE][SIZE=2][COLOR=#0000ff]Handles[/COLOR][/SIZE][SIZE=2] mnuWindowCloseAllOpenRecords.Click[/SIZE]
[SIZE=2][COLOR=#0000ff]    Dim[/COLOR][/SIZE][SIZE=2] indx [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Integer[/COLOR][/SIZE]
[SIZE=2][COLOR=#0000ff]    While [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Me[/COLOR][/SIZE][SIZE=2].MdiChildren.Length > 0[/SIZE]
[SIZE=2][COLOR=#0000ff]         Me[/COLOR][/SIZE][SIZE=2].MdiChildren(indx).Close()[/SIZE]
[SIZE=2][COLOR=#0000ff]    End [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]While[/COLOR][/SIZE]
 
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better?:

VB.NET: 
[SIZE=2][COLOR=#0000ff]Private [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Sub[/COLOR][/SIZE][SIZE=2] mnuWindowCloseAllOpenRecords_Click([/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] sender [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.Object, [/SIZE][SIZE=2][COLOR=#0000ff]ByVal[/COLOR][/SIZE][SIZE=2] e [/SIZE][SIZE=2][COLOR=#0000ff]As[/COLOR][/SIZE][SIZE=2] System.EventArgs) [/SIZE][SIZE=2][COLOR=#0000ff]Handles[/COLOR][/SIZE][SIZE=2] mnuWindowCloseAllOpenRecords.Click[/SIZE]
    Dim maxAttempts = Me.MdiChildren.Length 
    Dim attempts as Integer = 0
[SIZE=2][COLOR=#0000ff]   While [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]Me[/COLOR][/SIZE][SIZE=2].MdiChildren.Length > 0[/SIZE]
[SIZE=2][COLOR=#0000ff]        Me[/COLOR][/SIZE][SIZE=2].MdiChildren(0).Close()[/SIZE]
         attempts += 1
         if attempts > maxAttempts Then 
           MessageBox.Show("Attempt to close more forms than were ever open; maybe one has refused to close?")
           return
         end if
[SIZE=2][COLOR=#0000ff]   End [/COLOR][/SIZE][SIZE=2][COLOR=#0000ff]While[/COLOR][/SIZE]
 
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