Named Binary Tag serialization

using System;
using System.IO;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

using NBT.Tags;
using NBT.IO;

namespace NBT_Sample
{
    public partial class frmMain : Form
    {

        NBTFile nbtFile = new NBTFile();
        string filePath = Application.StartupPath + @"\test.nbt";

        public frmMain()
        {
            InitializeComponent();
        }

        private void frmMain_Load(object sender, EventArgs e)
        {
            if (File.Exists(this.filePath) == true)
            {
                this.nbtFile.Load(this.filePath);
                this.ReloadList();
            }
        }

        private void btnSave_Click(object sender, EventArgs e)
        {
            this.nbtFile.Save(this.filePath);
        }

        private void btnAdd_Click(object sender, EventArgs e)
        {
            this.nbtFile.RootTag.Add(this.txtKey.Text, new TagString(this.txtValue.Text));
            this.ReloadList();
        }
        private void ReloadList()
        {
            this.lstItems.Items.Clear();
            foreach (KeyValuePair<string, Tag> item in this.nbtFile.RootTag)
            {
                if (item.Value.GetType() == typeof(TagString))
                {
                    ListBoxItem lstItem = new ListBoxItem();
                    lstItem.Text = ((TagString)item.Value).value;
                    lstItem.Tag = item.Key;
                    this.lstItems.Items.Add(lstItem);
                }
            }
        }

        private void btnDelete_Click(object sender, EventArgs e)
        {
            if (this.lstItems.SelectedItems.Count > 0)
            { 
                ListBoxItem selectedItem = (ListBoxItem)this.lstItems.SelectedItem;
                this.nbtFile.RootTag.Remove((string)selectedItem.Tag);
                this.ReloadList();            
            }
        }
    }
}