I need to populate the TreeNode.ChildNodes on the event of TreeView.TreeNodeExpanded. The problem is the node is empty before the event gets fired and it is not expandable in this case and there is no expand icon [+] showed next to it.
I want to make the node expandable in case its related object has some children without adding those children to the node.
I thought about adding a virtual child to the node and delete it when it is expanded. Are there any better options ??
Thank you.
Three steps to do the trick:
1 - Set the TreeView.ExpandDepth to 0. This eliminates the expansion of the added TreeNode objects in the TreeView and shows the expansion symbol [+] next to each TreeNode that has the TreeNode.PopulateOnDemand property set to true.
2- Set the TreeNode.PopulateOnDemand to True for each branch TreeNode. When the TreeNode.ChildNodes collection is empty, the expansion symbol [+] will be showed only next to TreeNode objects that has TreeNode.PopulateOnDemand property set to true.
3- Handle the TreeView.TreeNodePopulate event to poulate branch nodes on expansion. This event will be fired when a TreeNode - with the TreeNode.PopulateOnDemand set to true - has been expanded right before the TreeView.TreeNodeExpanded event gets fired.
I suggest editing the template of the node. Have a look at An ASP.NET AJAX TreeView control with templates.
Not sure and do not have time to try but I guess what you are after is the TreeNode.PopulateOnDemand property and TreeView.TreeNodePopulate event.
Related
I have a tree view control that shows to the user the duplicated images files for two images folders, so when a duplication is found the app set the checkbox beside the tree view node to true.
It works fine but I can't prevent the user from altering the checkbox node values.
So, is it possible to disable the user altering to the checkbox for the tree view nodes, also is there other alternative control for the tree view control I can use instead?
Treeview is probably not what you want anyway.
However if this is Winforms (just a guess)
private void tree_BeforeCheck(object sender, TreeViewCancelEventArgs e)
{
e.Cancel = true;
}
Add pepper and salt to taste
TreeView.BeforeCheck Event
Occurs before the tree node check box is checked.
Furthermore
Setting the TreeNode.Checked property from within the BeforeCheck or
AfterCheck event causes the event to be raised multiple times and can
result in unexpected behavior. For example, you might set the Checked
property in the event handler when you are recursively updating the
child nodes, so that the user does not have to expand and check each
one individually. To prevent the event from being raised multiple
times, add logic to your event handler that only executes your
recursive code if the Action property of the TreeViewEventArgs is not
set to TreeViewAction.Unknown.
In my application i copy a certain pdf file to the selected node, after this i want the treeview to refresh and show me the added file.
The refresh is working but it won't expand the last selected node.
How can i do a refresh but still keep the last selected node expanded, so the user can see that the pdf file is added to the folder.
The AfterSelect on the TreeView have a parameter TreeViewEventArgs e. e.Node will return the selected node. eg:
e.Node.Expand();
or
e.Node.ExpandAll();
Should you wish to expand all the nodes in the treeview. You can use the same method to expand the
I assume that you know which node you have copied it too. Use the same method to expand the node you've copied too.
I want to create an expandable empty treenode in C#, i.e. a treenode which is empty and has the [+] sign beside it. The reason is because initially it is empty, but once a node is clicked, I want to populate it with many child nodes.
The only problem I am facing is that empty treenodes aren't expandable, so I don't know what to do. Is there a way to solve this problem, or are there any workarounds?
You have to redraw the tree itself, or create an empty node and simply remove it when the parent node is expanded.
Personally, I'd go for option b). I've done this before, a while ago and thanks to the events raised by the TreeView it pretty easy to accomplish.
You can give the empty node a value like 'Loading...' so it gives some feedback to the user as well. :)
Add a dummy child node, and remove it when you expand.
Have a look at Josh Smiths excellent tutorial on treeviews. It allows lazy loading of child tree nodes by having a dummy node that is removed upon expansion.
i have load a tree view. i want to Traverse treeview node and expand & select a node. Expand is working fine. but select a node is not working.
private void Traverse(TreeNodeCollection nodes, string findtext)
{
foreach (TreeNode node in nodes)
{
if (node.Text.ToString().Trim() == findtext)
{
node.Expand();
node.TreeView.SelectedNode = node.NextNode;
//tvwStructureTree.SelectedNode = this.tvwStructureTree.Nodes[node.Index];
//Select a node in Treeview tvwStructureTree But not working
tvwStructureTree.SelectedNode = node;
node.TreeView.Focus();
}
Traverse(node.Nodes, findtext);
}
}
Its in windows application.
Not quite sure what's your issue is. TreeView.SelectedNode Property is the correct property.
When you set this property, the specified node is scrolled into view
and any parent nodes are expanded so that the specified node is
visible.
When the parent node or any ancestor node of the selected node is
collapsed either programmatically or through user action, the
collapsed node becomes the selected node.
Make sure that the node.TreeView is the correct TreeView instance.
node.TreeView.SelectedNode = node.NextNode;
TreeView.HideSelection Property is another property that might useful for you.
When this property is set to false, selected nodes in the TreeView
control remain highlighted in a different color than the current
selection color when the TreeView control loses focus. You can use
this property to keep items that are selected by the user visible when
the user clicks a different control on the form or moves to a
different window.
I had a similar issue. My form's ctor is given the test of a node to select.Finding the correct node was not a problem, but the tree didn't show the node as selected, since the tree control didn't have focus. merely had to use Form.ActiveControl = myTreecontrol; before setting myTreecontrol.SelectedNode
I tested exactly your own code and worked fine, both find and selection the node!
without any particular property setting for my treeview!
by the way I am using .Net 3.5 and VS 2008
I Have Treeview (shown as above) in my app, I have binded it with collection...
now the problem is whenever I expand on Colorodo by default Aspen should get selected, means whenever I expand first item that Node should get selected..
Any Ideas/suggestion Please
Unfortunately, as I'm sure you have discovered, is that you cannot set the treeViewInstance.SelectedItem property as it's read-only.
From memory, each TreeViewItem has a IsSelected property that you can set. You try to listen for expand/collapse on the items and maybe set this property. Without trying this myself I don't know if it is a) a good solution b) if it would even works.
To get the TreeViewItem that is the container for the item in collection use
treeViewInstance.ItemContainerGenerator.ContainerFromItem(yourDataItem) as TreeViewItem;
Another idea (the way I would do it) is to use a ListBox/ListView and fake the hierarchical view. The create a view model controller and item, wrap your data, and manage this all yourself. If you want more information, please leave a comment and I will dig up a few examples to help.
HTH,
Dennis
There are two apporches choose what ever you like.
i) explore ItemTemplageSelector, not sure but may be possible to do work with it.
Other wise on tree expand event or mouse capture event get the Current Root node and then select its first child with index like rootNode.child[0]... set this is as Selected True or Isfocused and perfom operation that is intended on its click you you will make user feel like it is selected.