Simple Char Tree in C#

Tree.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace TestingConsole
{
    public class Node
    {
        private int Level { get; set; }
        private List<Node> Children { get; set; }

        public char Value { get; private set; }

        public Node()
        {
            Level = 0;
            Children = new List<Node>();
        }

        public Node(char value, int level)
        {
            Value = value;
            Level = level;
            Children = new List<Node>();
        }

        public static Node CreateTreeWithAllLetters()
        {
            var tree = new Node();

            for (int i = 'a'; i <= 'z'; i++)
            {
                tree.Insert(((char)i).ToString());
            }

            return tree;
        }

        public void Insert(string value)
        {
            InsertNode(value, 0);
        }

        private void InsertNode(string value, int index)
        {
            if (index >= value.Length) return;

            var letter = value[index];

            var correctChild = Children.Find(c => c.Value.Equals(letter));

            if (correctChild == null)
            {
                correctChild = new Node(letter, index + 1);
                Children.Add(correctChild);
            }

            correctChild.InsertNode(value, index + 1);
        }

        public string PrintHorizontally()
        {
            return PrintHorizontally(this, 0, 0);
        }

        private string PrintHorizontally(Node node, int level, int distanceFromStart)
        {
            var finalStr = "";

            if (node.Level != 0)
                finalStr += AddNodeToHorizontalString(node, distanceFromStart);

            foreach (var child in node.Children)
                finalStr += PrintHorizontally(child, level + 1, distanceFromStart + 1);

            return finalStr;
        }

        private static string AddNodeToHorizontalString(Node node, int distanceFromStart)
        {
            var distanceStr = "";

            for (int i = 0; i < distanceFromStart; i++)
                distanceStr += "| ";

            return $"{distanceStr}{node.Value}\n";
        }

        public override string ToString() => Value.ToString();
    }
}