ByVal TreeView Modifies Original?

[casManG]

I am working on a small project that uses the treeview control in
vb.net 2003. I have a tree view that I am sending to a sub in order to
iterate through the nodes.

Public Sub test (ByVal inTreeView as Tree View)

But, the thing I want to do with the inTreeView requires me to expand
all the nodes before I iterate. The problem is that when the sub is
complete, the original tree view on my form ends up with all of the
nodes expanded I had hoped that sending it to my sub "ByVal" would
make a copy that I could mess around with without effecting the
original. I also tried creating a new treeview and assigning the
inTreeView to it, then doing my stuff:

dim TestTree as new TreeView
TestTree = inTreeView

but no matter what the source treeview always gets expanded when I do
an expandall TestTree.ExpandAll()

Can anyone tell me how to get a duplicate of a treeview in a way that
I can expandall and not effect the source object?

Thanks
cas

 

[Jon Skeet [C# MVP]]

I am working on a small project that uses the treeview control in
vb.net 2003. I have a tree view that I am sending to a sub in order to
iterate through the nodes.

Public Sub test (ByVal inTreeView as Tree View)

But, the thing I want to do with the inTreeView requires me to expand
all the nodes before I iterate. The problem is that when the sub is
complete, the original tree view on my form ends up with all of the
nodes expanded I had hoped that sending it to my sub "ByVal" would
make a copy that I could mess around with without effecting the
original. I also tried creating a new treeview and assigning the
inTreeView to it, then doing my stuff:

dim TestTree as new TreeView
TestTree = inTreeView

but no matter what the source treeview always gets expanded when I do
an expandall TestTree.ExpandAll()

Yes. You need to understand what it means to pass a reference by value.
See http://pobox.com/~skeet/csharp/parameters.html - it talks in C#
terms, but if you understand that the C# default is "ByVal" and "ref"
corresponds to "ByRef" it should still be useful.

Can anyone tell me how to get a duplicate of a treeview in a way that
I can expandall and not effect the source object?

You'll need two completely separate object, which should have
completely different objects underneath, I strongly suspect (i.e. they
won't actually share nodes).

Unfortunately TreeView doesn't provide a Clone method - I suspect
you'll have to create a new TreeView and then populate it by traversing
the "old" one and adding nodes with the same values to the new
TreeView.

 

[casManG]

Yes. You need to understand what it means to pass a reference by value.
Seehttp://pobox.com/~skeet/csharp/parameters.html- it talks in C#
terms, but if you understand that the C# default is "ByVal" and "ref"
corresponds to "ByRef" it should still be useful.


You'll need two completely separate object, which should have
completely different objects underneath, I strongly suspect (i.e. they
won't actually share nodes).

Unfortunately TreeView doesn't provide a Clone method - I suspect
you'll have to create a new TreeView and then populate it by traversing
the "old" one and adding nodes with the same values to the new
TreeView.

Ok, thank you for your help Jon