Save the state of a TreeView

[Flyguy]

I have a DataSource and a TreeView that I am rebinding. When I do this the
TreeView will close all of its nodes. Is there a way that I can save the
state of the TreeViews nodes so that I can reapply it after the rebinding
takes effect?

// Save the state of treeView
dataSource.DataBind();
treeView.DataBind();
//reapply the state so the treeView will be opened to the same node as it was.

 

[Steven Cheng[MSFT]]

Hi Flyguy,

From your description, you have ASP.NET web pages that use TreeView
control(bound to datasource), however, you find that whenever you rebind
the Treeview with the DataSource, the TreeNodes status(such as expand ,
collapse) will lost, you're looking for some means to keep such status,
correct?

As for the rebinding, how did it happen, is it due to the redirection
during page navigation? For such navigation case, you can consider use
separate frame pages to hold the TreeView navigation menu so as to avoid
reload/rebind on each redirection.

If the problem is due to other things, I think you can try the following
means for keep node status:

**ASP.NET TreeView control's "Nodes" property is a TreeNodeCollection, you
can copy it to an array and cache the array in memory(through cache or
session...)

** When page reload and TreeView rebind, you can loop through the cached
Node Array and assign the proper node status (for the corresponding nodes).

How do you think?

Sincerely,

Steven Cheng

Microsoft MSDN Online Support Lead



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--------------------

 

[Louis Somers]

Flyguy schreef:

I have a DataSource and a TreeView that I am rebinding. When I do this the
TreeView will close all of its nodes. Is there a way that I can save the
state of the TreeViews nodes so that I can reapply it after the rebinding
takes effect?

// Save the state of treeView
dataSource.DataBind();
treeView.DataBind();
//reapply the state so the treeView will be opened to the same node as it was.

DataBind basically throws the treeview internals away and creates a new one from the DataSet. This
way all treeview specific data such as expand-state is lost. To update the data without losing the
state, you will have to synchronize the treeview with your dataset yourself instead of using the
built in DataBind() function.

Synchronizing involves recursively iterating, removing old items and adding new ones. It helps if
the data is sorted, you may be able to take shortcuts if you know what has happened to the data
before synchronizing (items only removed, or only added e.g.)

Cheers,
Louis

 

[LRuss]

Hello Steve.

You say "you can consider use separate frame pages to hold the TreeView
navigation menu". Are you suggesting the use of framesets? As I understand
it, ASP.NET does not support framesets. Can you elaborate?

Thanks,
Len Russell