multiselect treenode

Selecting multiple nodes in treevieiw

Source code of my example can be found here:

Download multipleTreeNodeSelect2.zip - 37.21 KB

If you're working with treeviews wishing that you had a multiple node select feature, this code is just meant for you. Most of the articles that i read in the internet either suggested me to use some custom tree control or the suggested codes seemed real complex to me. Hence i wrote the code myself so that anyone willing to use this feature could do it in their existing tree views without having to retort to custom controls.

Background

The idea behind the code is simple, I've globally maintained a List of treenodes. When the user clicks a node, any modifier key like Ctrl is checked if pressed. If no modifier key is found to be pressed, the list is cleared and the node is added to the list. If there is a Ctrl key is pressed, then we add the node to the list, In the end, i've put up a function which paints the tree such that only those node present in the list are highlighted.

Using the code

The function below, treeView1_BeforeSelect(object sender, TreeViewCancelEventArgs e) is called before any node in the treeview is selected. Another important line of code is, e.Cancel = true;. Without this code, when we deselect the node, the windows function paints it once again. As a result the treeview nodes doesnt change colors as expected. Canceling this event argument, prevents the windows from repainting the node as selected one.

        private void treeView1_BeforeSelect(object sender, TreeViewCancelEventArgs e)
        {
            if (ModifierKeys == Keys.Control)
            {
                if (trSelectedNodes.Contains(e.Node))
                    trSelectedNodes.Remove(e.Node);
                else trSelectedNodes.Add(e.Node);
            }
            else
            {
                trSelectedNodes.Clear();
                trSelectedNodes.Add(e.Node);
            }
            trPaintSelected();
            showSelectedInBox();
            e.Cancel = true;
        }		

Alternatives

This can also be done, by writing the same thing on the NodeMouseClick() function :) I shall post the code soon.

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