Controls.Add('fixed control type')

Question

I've make a UserControl and want only buttons can be added to its ControlCollection, if others controls are added, it will throw an exception.

Can this work?

Answer 1

Im not sure if this is what you looking for but try it
Dim cont As Control
 If cont.GetType.Name = "Button" Then
 Me.Controls.Add(cont)
Else
MsgBox("invalid control,button only")
 End If

kaymaf

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If that what you want, take it. If not, ignored it and no complain

Answer 2

    Private Sub UserControl1_ControlAdded( _
    ByVal sender As System.Object, _
    ByVal e As System.Windows.Forms.ControlEventArgs) _
    Handles MyBase.ControlAdded

        If Not TypeOf e.Control Is Button Then
            Me.Controls.Remove(e.Control)
            MessageBox.Show("Button Controls only", _
                            "Control add error", _
                            MessageBoxButtons.OK, _
                            MessageBoxIcon.Error)
        End If

    End Sub

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coding for fun Be a good forum member mark posts that contain the answers to your questions or those that are helpful
Please format the code in your posts with the button . Makes it easier to read .

Answer 3

    Private Sub UserControl1_ControlAdded(ByVal sender As Object, ByVal e As System.Windows.Forms.ControlEventArgs) Handles Me.ControlAdded
        If Not TypeOf e.Control Is Button Then
            Me.Controls.Remove(e.Control)
            MsgBox("Invalid Control")
        End If
    End Sub

Edit: stabbed by bdbodger

lol, I wasted too much time editing posts

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Thanks

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Answer 4

Hi there,

actually, this sort of task is usually performed by means of a designer which is then applied to your UserControl. For instance, if you'd be developing your own TabControl, you'd only want to allow TabPages to be dropped into the TabControl-container. In this case, you would create a new class that inherits from ParentControlDesigner (which resides in the System.Windows.Forms.Design namespace). In this class, overriding the CanParent function and returning true only if the type of the control passed is on your "list" of allowed controls (like, for the TabControl, a TabPage) would do exactly what you want.
The designer-class is also the place where you add all the stuff you might need in order to provide your UserControl-consumers with the so-called "design time experience", i.e. how drag'n'drop is performed, what properties might have to be removed or whether there should be that little arrow on your control that allows consumers to perform certain tasks (i.e., sticking with the TabControl, adding or removing TabPages).

That said, at design-time, there wouldn't have to be an exception in the first place due to the fact that the control simply wouldn't accept anything but the desired control(s). It would trigger an exception at run-time though, i.e. if you were adding controls via code.

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Cheers,
Olaf