TreeView tree = new ()
{
    Width = 40,
    Height = 20
};

TreeNode root1 = new () { Text = "Root1" };
root1.Children.Add (new TreeNode { Text = "Child1.1" });
root1.Children.Add (new TreeNode { Text = "Child1.2" });

TreeNode root2 = new () { Text = "Root2" };
root2.Children.Add (new TreeNode { Text = "Child2.1" });
root2.Children.Add (new TreeNode { Text = "Child2.2" });

tree.AddObject (root1);
tree.AddObject (root2);

├-Root1
│ ├─Child1.1
│ └─Child1.2
└-Root2
  ├─Child2.1
  └─Child2.2

TreeView<GameObject> tree = new ()
{
    Width = 40,
    Height = 20,
    TreeBuilder = new DelegateTreeBuilder<GameObject> (
        childGetter: o => o is Army a ? a.Units : Enumerable.Empty<GameObject> (),
        canExpand: o => o is Army)
};

tree.AddObject (new Army
{
    Designation = "3rd Infantry",
    Units = [new Unit { Name = "Orc" }, new Unit { Name = "Troll" }]
});

class GameObjectTreeBuilder : ITreeBuilder<GameObject>
{
    public bool SupportsCanExpand => true;

    public bool CanExpand (GameObject model) => model is Army;

    public IEnumerable<GameObject> GetChildren (GameObject model)
    {
        if (model is Army a)
        {
            return a.Units;
        }

        return Enumerable.Empty<GameObject> ();
    }
}

tree.TreeBuilder = new DelegateTreeBuilder<GameObject> (
    childGetter: o => o is Army a ? a.Units : Enumerable.Empty<GameObject> (),
    canExpand: o => o is Army);

class House : TreeNode
{
    public string Address { get; set; } = "";
    public List<Room> Rooms { get; set; } = [];

    public override IList<ITreeNode> Children => Rooms.Cast<ITreeNode> ().ToList ();
    public override string Text { get => Address; set => Address = value; }
}

class Room : TreeNode
{
    public string Name { get; set; } = "";
    public override string Text { get => Name; set => Name = value; }
}

tree.AddObject (new House
{
    Address = "23 Nowhere Street",
    Rooms = [new Room { Name = "Ballroom" }, new Room { Name = "Bedroom" }]
});

tree.Accepting += (sender, e) =>
                  {
                      // Fires on Enter key or double-click
                      // Set e.Cancel = true to prevent Accepted from firing
                  };

tree.Accepted += (_, _) =>
                 {
                     // Node was accepted (confirmed)
                     ITreeNode? selected = tree.SelectedObject;
                 };

tree.SelectionChanged += (sender, e) =>
                         {
                             // e.OldValue is the previously selected object
                             // e.NewValue is the newly selected object
                         };

tree.DrawLine += (sender, e) =>
                 {
                     // e.Model is the object being drawn
                     // e.IndexOfModelText is the column where text starts
                     // e.Cells is the list of cells to render
                     // Set e.Handled = true to suppress default rendering
                 };

treeViewFiles.AspectGetter = f => f.FullName;

tree.ColorGetter = node =>
                   {
                       if (node is HiddenFile)
                       {
                           return new Scheme { Normal = new Attribute (Color.Gray, Color.Black) };
                       }

                       return null; // Use default scheme
                   };

tree.MultiSelect = true;

tree.AllowLetterBasedNavigation = false;

tree.Filter = new TreeViewTextFilter<FileSystemInfo> (tree)
{
    Text = "*.cs"
};

class MyFilter : ITreeViewFilter<GameObject>
{
    public bool IsMatch (GameObject model) => model.ToString ().Contains ("Orc");
}

TreeNode parent = (TreeNode)tree.SelectedObject!;
parent.Children.Add (new TreeNode { Text = "New Child" });
tree.RefreshObject (parent);

ITreeNode toDelete = tree.SelectedObject!;

if (tree.Objects.Contains (toDelete))
{
    // It's a root node
    tree.Remove (toDelete);
}
else
{
    // It's a child node — remove from parent's children
    ITreeNode? parent = tree.GetParent (toDelete);
    parent?.Children.Remove (toDelete);
    tree.RefreshObject (parent);
}