TreeView feature to uncheck all other nodes

This is the feature i want to implement:

1. check a tree node by click mouse as normal, user can multiple select.

2. when user hold Ctrl+ mouse, i want the tree node which mouse clicked to be checked and all other nodes are unchecked.

I have a version but it is not elegant:

Any suggestions?

If you want to test the code, replace TreeViewAdv and TreeNodeAdv with normal TreeView and TreeNode.

using Syncfusion.Windows.Forms.Tools; namespace treeviewtest { public partial class Form1 : Form { TreeNodeAdv CurrentNode = null; public Form1() { InitializeComponent(); } private void treeViewAdv1_AfterCheck(object sender, Syncfusion.Windows.Forms.Tools.TreeNodeAdvEventArgs e) { TreeViewAdv tree = sender as TreeViewAdv; if (Control.ModifierKeys == Keys.Control && e.Action!= TreeViewAdvAction.Unknown) { foreach (TreeNodeAdv node in tree.Nodes) { if (node.CheckState == CheckState.Checked && node != CurrentNode) node.Checked = false; foreach (TreeNodeAdv n in node.WalkTree()) { if (n.CheckState == CheckState.Checked && n != CurrentNode) n.Checked = false; } } } CurrentNode = null; } private void treeViewAdv1_BeforeCheck(object sender, TreeNodeAdvBeforeCheckEventArgs e) { if (Control.ModifierKeys == Keys.Control && CurrentNode == null) { CurrentNode = e.Node; if (e.NewCheckState == CheckState.Unchecked) { TreeViewAdv tree = sender as TreeViewAdv; foreach (TreeNodeAdv node in tree.Nodes) { if (node.CheckState == CheckState.Checked && node != CurrentNode) node.Checked = false; foreach (TreeNodeAdv n in node.WalkTree()) { if (n.CheckState == CheckState.Checked && n != CurrentNode) n.Checked = false; } } e.Cancel = true; } } } } public static class externtree { public static IEnumerable<TreeNodeAdv> WalkTree(this TreeNodeAdv node) { if (node == null) yield break; // return itself first yield return node; // return children if (node.HasChildren) { foreach (TreeNodeAdv cNode in node.Nodes) foreach (TreeNodeAdv iNode in cNode.WalkTree()) yield return iNode; } } } }