Copying/Cloning a control

[=?Utf-8?B?Sm9uIEVsbGlz?=]

Hi All,

I want to implement an 'generic' undo by placing a copy of a control in a
stack using System.Collecti ons.Generic.Sta ck. Basically this way I don't need
to know if a user has edited text in tree, added or deleted a node etc,
added items to a list box etc etc. I just push the control onto the stack
when they change it (regardless of control type) and Pop if back if they undo.

My problem is how to a get a copy of the control? Obviosuly if I push the
control onto the stack, I get a reference to the original so every entry on
the stack is always the same, so I need to make a copy of the control that is
independant of the original.

Is there an *easy* way to do this - I've found a few examples, but they seem
dependant on knowing exactly what type of control it is, and wind through all
the properties etc, I was hoping for something more generic.

I am using VB.Net 2005.

Thanks in advance!


--
Jon

[Robin Tucker]

Re: Copying/Cloning a control

Hi Jon,

I don't think this idea is very good to be honest. There is a lot of
plumbing associated with a control that is just superfluous in an undo-redo
context - especially in a tree view where you are only interested in what
happened to the last node (i.e. subtree).

It's easy to create a structure for undo-redo where you do know precisely
what action occurred. Create a simple class hierarchy with overridable
method "Undo" and "Redo" - it's also useful to add in "CanUndo" and
"CanRedo", along with a "Size" and "Label" property (so you can know how
much space your undo-redo stack is taking up and can possibly tell the user
what the undo/redo action will do). Keep state information in the instance.
When the user deletes a node, you add a "NodeDelete d" class instance onto
your stack. When he inserts a node, you add a "NodeInsert ed" class
instance. Both of these are derived from your undo-redo base class.

Thestructure can be used in other contexts. For example if you are deleting
from a listview, where that node is also present in the tree, you still only
need the 1 undo-redo instance.



Robin

[=?Utf-8?B?cnViZW4=?=]

RE: Copying/Cloning a control

Just trying to help in the control cloning because I recently need it.
I developed the following function but at the end I didn't use it because I
changed my mind about cloning.

Private Function CloneControl(By Val Ctrl As Control, ByVal Parent As
Object) As Control
Try
Dim CtrlType As Type = Ctrl.GetType()
Dim CtrlObject As Object = Activator.Creat eInstance(CtrlT ype)
Dim CtrlNew As Control = CtrlObject

Dim pdcCtrl As
System.Componen tModel.Property DescriptorColle ction =
System.Componen tModel.TypeDesc riptor.GetPrope rties(Ctrl)
Dim pdcCtrlNew As
System.Componen tModel.Property DescriptorColle ction =
System.Componen tModel.TypeDesc riptor.GetPrope rties(CtrlNew)
For i As Integer = 0 To pdcCtrl.Count - 1
If pdcCtrl(i).Name = "Parent" Then
CtrlNew.Parent = Parent

ElseIf pdcCtrl(i).Name = "Controls" Then
If Not Ctrl.Controls Is Nothing Then
For Each CtrlChild As Control In Ctrl.Controls
CtrlNew.Control s.Add(CloneCont rol(CtrlChild,
CtrlNew))
Next
End If

Else
pdcCtrlNew(i).S etValue(CtrlNew , pdcCtrl(i).GetV alue(Ctrl))
End If
Next

Return CtrlNew

Catch ex As Exception
Return Nothing
End Try
End Function

ex. calling the function:
Dim tb as TextBox
tb = CloneControl(Te xtBox1, Nothing)

Hope this helps!

"Jon Ellis" wrote:

Hi All,
>
I want to implement an 'generic' undo by placing a copy of a control in a
stack using System.Collecti ons.Generic.Sta ck. Basically this way I don't need
to know if a user has edited text in tree, added or deleted a node etc,
added items to a list box etc etc. I just push the control onto the stack
when they change it (regardless of control type) and Pop if back if they undo.
>
My problem is how to a get a copy of the control? Obviosuly if I push the
control onto the stack, I get a reference to the original so every entry on
the stack is always the same, so I need to make a copy of the control that is
independant of the original.
>
Is there an *easy* way to do this - I've found a few examples, but they seem
dependant on knowing exactly what type of control it is, and wind through all
the properties etc, I was hoping for something more generic.
>
I am using VB.Net 2005.
>
Thanks in advance!
>
>
--
Jon

[=?Utf-8?B?Sm9uIEVsbGlz?=]

RE: Copying/Cloning a control

Ruben,

Thanks for the response, but the following line just generates a an error (A
first chance exception of type 'System.Compone ntModel.Win32Ex ception'
occurred in System.dll) repeatedly -

pdcCtrlNew(i).S etValue(CtrlNew , pdcCtrl(i).GetV alue(Ctrl))

Think I'm going give up on the idea; just thought it would be a neat way of
implementing do/undo for any control.

--
Jon


"ruben" wrote:

Just trying to help in the control cloning because I recently need it.
I developed the following function but at the end I didn't use it because I
changed my mind about cloning.
>
Private Function CloneControl(By Val Ctrl As Control, ByVal Parent As
Object) As Control
Try
Dim CtrlType As Type = Ctrl.GetType()
Dim CtrlObject As Object = Activator.Creat eInstance(CtrlT ype)
Dim CtrlNew As Control = CtrlObject
>
Dim pdcCtrl As
System.Componen tModel.Property DescriptorColle ction =
System.Componen tModel.TypeDesc riptor.GetPrope rties(Ctrl)
Dim pdcCtrlNew As
System.Componen tModel.Property DescriptorColle ction =
System.Componen tModel.TypeDesc riptor.GetPrope rties(CtrlNew)
For i As Integer = 0 To pdcCtrl.Count - 1
If pdcCtrl(i).Name = "Parent" Then
CtrlNew.Parent = Parent
>
ElseIf pdcCtrl(i).Name = "Controls" Then
If Not Ctrl.Controls Is Nothing Then
For Each CtrlChild As Control In Ctrl.Controls
CtrlNew.Control s.Add(CloneCont rol(CtrlChild,
CtrlNew))
Next
End If
>
Else
pdcCtrlNew(i).S etValue(CtrlNew , pdcCtrl(i).GetV alue(Ctrl))
End If
Next
>
Return CtrlNew
>
Catch ex As Exception
Return Nothing
End Try
End Function
>
ex. calling the function:
Dim tb as TextBox
tb = CloneControl(Te xtBox1, Nothing)
>
Hope this helps!
>
"Jon Ellis" wrote:
>

Hi All,

I want to implement an 'generic' undo by placing a copy of a control in a
stack using System.Collecti ons.Generic.Sta ck. Basically this way I don't need
to know if a user has edited text in tree, added or deleted a node etc,
added items to a list box etc etc. I just push the control onto the stack
when they change it (regardless of control type) and Pop if back if they undo.

My problem is how to a get a copy of the control? Obviosuly if I push the
control onto the stack, I get a reference to the original so every entry on
the stack is always the same, so I need to make a copy of the control that is
independant of the original.

Is there an *easy* way to do this - I've found a few examples, but they seem
dependant on knowing exactly what type of control it is, and wind through all
the properties etc, I was hoping for something more generic.

I am using VB.Net 2005.

Thanks in advance!


--
Jon

[Cor Ligthert [MVP]]

Re: Copying/Cloning a control

Jon,

Like Robin I don't think it is a good idea, however the only way I know how
to do it is serializing and deserializing.

http://www.vb-tips.com/dbpages.aspx?ID=7ffd296f-9e81-47e6-88dc-61641f5c8d9d

Cor


"Jon Ellis" <JonEllis@discu ssions.microsof t.comschreef in bericht
news:FB150EBE-4A7B-4624-B1DE-019E6E8030C0@mi crosoft.com...

Hi All,
>
I want to implement an 'generic' undo by placing a copy of a control in a
stack using System.Collecti ons.Generic.Sta ck. Basically this way I don't
need
to know if a user has edited text in tree, added or deleted a node etc,
added items to a list box etc etc. I just push the control onto the stack
when they change it (regardless of control type) and Pop if back if they
undo.
>
My problem is how to a get a copy of the control? Obviosuly if I push the
control onto the stack, I get a reference to the original so every entry
on
the stack is always the same, so I need to make a copy of the control that
is
independant of the original.
>
Is there an *easy* way to do this - I've found a few examples, but they
seem
dependant on knowing exactly what type of control it is, and wind through
all
the properties etc, I was hoping for something more generic.
>
I am using VB.Net 2005.
>
Thanks in advance!
>
>
--
Jon