Playing around with the TreeView

Playing around with the ASP.Net TreeView.

Initially a TreeNode is created and child nodes are added under the node.

        TreeNode tree = new TreeNode();

        

        tree.Value = "Social Media";

        tree.ImageUrl = "/images/home.png";

        tree.ChildNodes.Add(new TreeNode("Facebook", "Facebook","/images/fb.png"));

        tree.ChildNodes.Add(new TreeNode("G+","GPlus","/images/google.png"));

        tree.ChildNodes.Add(new TreeNode("Printrest", "Printrest", "/images/pintrest.png"));

        tree.ChildNodes.Add(new TreeNode("Twitter", "Twitter", "/images/twitter.jpg"));

Now lets add some child nodes under the created nodes. In this example the below would be the leaf nodes.

            foreach (TreeNode node in tree.ChildNodes)

            {

                node.ChildNodes.Add(new TreeNode("Sri Lanka", string.Concat(node.Value,"-","SL"), "/images/countries/SL-flag.jpg"));
                node.ChildNodes.Add(new TreeNode("Malaysia", string.Concat(node.Value,"-","ML"), "/images/countries/malaysia-flag.png"));
                node.ChildNodes.Add(new TreeNode("USA", string.Concat(node.Value,"-","USA"), "/images/countries/US-Flag.png"));
                node.ChildNodes.Add(new TreeNode("Britain", string.Concat(node.Value,"-","BRIT"), "/images/countries/Britain-flag.png"));
                node.ChildNodes.Add(new TreeNode("Australia", string.Concat(node.Value,"-","AUS"), "/images/countries/Australia-Flag.png"));
                node.ChildNodes.Add(new TreeNode("Netherlands", string.Concat(node.Value,"-","NL"), "/images/countries/netherlands-flag.png"));
                node.ChildNodes.Add(new TreeNode("Egypt", string.Concat(node.Value,"-","EG"), "/images/countries/Egypt-Flag.png"));
                node.ChildNodes.Add(new TreeNode("Greece", string.Concat(node.Value,"-","GR"), "/images/countries/greece_flag.png"));
                node.ChildNodes.Add(new TreeNode("Germany", string.Concat(node.Value,"-","GE"), "/images/countries/germany-flag.png"));
                node.ChildNodes.Add(new TreeNode("Canada", string.Concat(node.Value,"-","CA"), "/images/countries/canada_flag.png"));
                node.ChildNodes.Add(new TreeNode("Brazil", string.Concat(node.Value,"-","BR"), "/images/countries/brazil-flag.png"));

            }

 The TreeNode is then set to a TreeView to be displayed in the Form.

        TreeView view = new TreeView();

        view.ShowCheckBoxes = TreeNodeTypes.All;

        view.Nodes.Add(tree);

        view.TreeNodeCheckChanged += view_TreeNodeCheckChanged;

        view.Attributes.Add("onclick", "postBackByObject()");

        form1.Controls.Add(view);

Here, notice the JavaScript method postBackByObject() which does the job of auto postbacking on clicking on a Checkbox of a Node. For this purpose you need to add the following script in the ASPX page. Auto post backing comes in handy when you need to check or uncheck the set of child-nodes belonging to a selected node.

    <script type="text/javascript">

        function postBackByObject() {

            var o = window.event.srcElement;

            if (o.tagName == "INPUT" && o.type == "checkbox") {

                __doPostBack("", "");

            }

        }

    </script>

To programmatically check or uncheck child nodes of a node, use the TreeNodeCheckChanged event. A sample code would be:

    void view_TreeNodeCheckChanged(object sender, TreeNodeEventArgs e)

    {

        if (e.Node.Checked)

        {

            CheckChildNodes(e.Node.ChildNodes);

        }

        else if (e.Node.Checked == false)

        {

            UncheckChildNodes(e.Node.ChildNodes);

        }

    }

    private void UncheckChildNodes(TreeNodeCollection children)

    {

        foreach (TreeNode child in children)

        {

            if (child.Checked)

                child.Checked = false;

            UncheckChildNodes(child.ChildNodes);

        }

    }

    private void CheckChildNodes(TreeNodeCollection children)

    {

        foreach (TreeNode child in children)

        {

            if (child.Checked == false)

                child.Checked = true;

            CheckChildNodes(child.ChildNodes);

        }

    }

Then you get the resulting tree as below. The data in this view is created merely for illustration purposes of the ASP.Net TreeView and has no actual meaning.