NodeCheckBox node control

NodeCheckBox nodecontrol = new NodeCheckBox();
nodecontrol.AttachTo(tree);
 
Node node = new Node(“node title”);
node.CheckState = eCheckState.Checked;
// define the check type for every node.
node.CheckType = eCheckType.RadioButton            // or eCheckType. CheckBox
node.AttachTo(tree);

// the node control instance to access it from the event handler later.
private NodeCheckBox checkBox;
 
// create the node control.
checkBox = new NodeCheckBox();
checkBox.AttachTo(tree);
 
// create the node.
Node node = new Node();
node.AttachTo(tree);
 
tree.MouseDown += tree_MouseDown;
 
// process the mouse click on a node.
void tree_MouseDown(FlexibleTreeView pTreeview, MouseActionArgs pArgs)
{
  if (pArgs.NodeControl == checkBox)
  {
    // change the check state manually
    pArgs.Node.CheckState = checkBox.GetNextCheckState(pArgs.Node);
 
    // and skip all further treeview`s actions for this event.
    pArgs.Handled = true;
  }
}

// Custom node control class where we manually replace the Checked check state with Unknown when node`s check state has changed.
class MyNodeCheckBox : NodeCheckBox
{
  // override the check state change logic and replace the Checked state with Unknown.
  protected override void SetNextCheckState(Node pNode)
  {
    // Checked or Unknown –> Unchecked.
    if (pNode.CheckState == eCheckState.Unknown)
    {
      pNode.CheckState = eCheckState.Unchecked;
    }
    // Unchecked –> Unknown.
    else
    {
      pNode.CheckState = eCheckState.Unknown;
    }
  }
}
 
// create our node control.
MyNodeCheckBox nc = new MyNodeCheckBox();
nc.AttachTo(tree);
 
Node node = new Node();
// enable the three check states feature to be able to change to the Unknown state in our node control.
node.ThreeCheckState = true;
node.AttachTo(tree);

// change the icon of the checkbox in unchecked state.
tree.Images.CheckboxUnchecked = myUncheckedIcon;
// change the icon of the radio button in checked state.
tree.Images.RadioButtonChecked = myCheckedIcon;