BreadthTraverse gets stuck somewhere. When I use the debug feature, Visual Studio hits an error and closes after line 173.

BinarySearchTree.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace BinaryTree
{
    class Program
    {
        static void Main(string[] args)
        {
            var newBST = new BSTNode<int>();
            newBST.Add(12);
            newBST.Add(6);
            newBST.Add(18);
            newBST.Add(3);
            newBST.Add(14);
            newBST.Add(9);
            newBST.Add(17);

            newBST.PrintString();
        }
    }

    public class BSTNode<T> where T : IComparable<T>
    {
        public T Value { get; set; }
        public BSTNode<T> Right { get; protected set; }
        public BSTNode<T> Left { get; protected set; }
        public bool Printed { get; protected set; }
        public int Count { get; protected set; } = 0;

        public void Add(T newValue)
        {

            var newNode = new BSTNode<T>();

            //If this node does not hold a value, set it to the value currently being added. If the node equals 0, increment the Count at this node.
            if (Value == null || Value.Equals(0))
            {
                if (Value.Equals(newValue))
                {
                    Count += 1;
                }
                Value = newValue;
            }
            //If there is a value in the node, or the base node value is not 0, compare the new value to the current node value.
            //Either increment the count by 1, or determine if child node [left or right] exists.
            //Call Add with the newValue on the (possibly newly created) [left or right] node.
            else
            {
                switch (Value.CompareTo(newValue))
                {
                    case 0:
                        Count += 1;
                        break;
                    case -1:
                        if (Left == null)
                        {
                            Left = newNode;
                        }
                        Left.Add(newValue);
                        break;
                    case 1:
                        if (Right == null)
                        {
                            Right = newNode;
                        }
                        Right.Add(newValue);
                        break;
                    default:
                        break;
                }
            }
        }

        public string PrintString()
        {
            var toPrint = new StringBuilder();
            if (Left != null)
            {
                Left.PrintString();
            }
            else
            {
                for (int i = Count; i > 0; i--)
                {
                    toPrint.Append(Value + ", ");
                }
                if (Right != null)
                {
                    for (int i = Count; i > 0; i--)
                    {
                        toPrint.Append(Value + ", ");
                    }
                }
            }



            return toPrint.ToString();
        }






    }
















}