C# code to generate tree objects from list of addresses. Item in list looks like "root.child1.child2.child3"

TreeFromList.cs

public abstract class BranchNode
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Path { get; set; }
    [NotMapped]
    public string ParentPath
    {
        get
        {
            var lastDotPosition = Path.LastIndexOf('.');
            return lastDotPosition == -1 ? null : Path.Substring(0, lastDotPosition );
        }
        set => throw new System.NotImplementedException();
    }

    [NotMapped]
    public IEnumerable<BranchNode> Children { get; set; }
}


public static class TreeExtension
{
    public static T GetParentNode<T>(this IEnumerable<T> collection,
        T current) where T : BranchNode
    {
        return collection.FirstOrDefault(node => node.Path == current.ParentPath);
    }

    public static IEnumerable<T> GenerateTree<T>(this IEnumerable<T> table, T rootNode) where T : BranchNode
    {
        var organizationalNodes = table.ToList();
        var rootNodes = organizationalNodes.Where(node => node.ParentPath == rootNode?.Path).ToList();

        foreach (var node in rootNodes)
        {
            node.Children = organizationalNodes.GenerateTree(node);
        }

        return rootNodes;
    }
}
    
// usage

var result = await _context.GetItemsAsync<TerritorialNode>();
result.GenerateTree( null);