TrieNode.cs

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

namespace PrefixTree {
  public class TrieNode : Hashtable {
    private TrieNode parent;
    private char? value;

    public TrieNode(char? value = null, TrieNode parent = null)
      : base() {
      this.parent = parent;
      this.value = value;
    }

    public bool EndsWord {
      get;
      set;
    }

    public TrieNode this[char key] {
      get { return base[key] as TrieNode; }
      set { base[key] = value; }
    }

    public TrieNode FindOrCreate(char ch) {
      return this[ch] = this[ch] ?? new TrieNode( ch, this );
    }

    public void ToList(ref List<string> wordList) {
      foreach( TrieNode node in Values ) {
        if( node.EndsWord )
          wordList.Add( node.ToString() );

        node.ToList( ref wordList );
      }
    }

    public override string ToString() {
      return String.Concat( parent == null ? "" : parent.ToString(), this.value );
    }
  }
}