c#从我的XML文件中填充树视图，同时过滤它以避免重复

    /// <summary>
    /// Initalizes Tree View
    /// </summary>
    private void InitializeTreeView()
    {
        var mappingList = ReadXmlData();
        BuildTree(mappingList);
    }
    /// <summary>
    /// Reads Mappings from xml file to a List
    /// </summary>
    /// <returns></returns>
    private List<Mapping> ReadXmlData()
    {
        var mappingList = new List<Mapping>();
        var reader = new XmlTextReader(@"D:'data.xml");
        while (reader.Read())
        {
            reader.ReadToFollowing("system");
            string system = reader.ReadString();
            reader.ReadToFollowing("subsystem");
            string subSystem = reader.ReadString();
            reader.ReadToFollowing("subsubsystem");
            string subSubSystem = reader.ReadString();
            mappingList.Add(new Mapping() { _system = system, _subSystem = subSystem, _subSubSystem = subSubSystem });
        }
        return mappingList;
    }
    /// <summary>
    /// Builds Tree
    /// </summary>
    /// <param name="mappingList"></param>
    private void BuildTree(List<Mapping> mappingList)
    {
        foreach (var mapping in mappingList)
        {
            var systemNode = FindNode(mapping._system, NodeType.System);
            if (string.IsNullOrEmpty(systemNode.Text))
            {
                string nodeText = NodeType.System.ToString() + " - " + mapping._system; ;
                systemNode.Text = nodeText;
                systemNode.Name = nodeText;
                treeView1.Nodes.Add(systemNode);
            }
            var subSystemNode = FindNode(mapping._subSystem, NodeType.SubSystem);
            if (string.IsNullOrEmpty(subSystemNode.Text))
            {
                string nodeText = NodeType.SubSystem.ToString() + " - " + mapping._subSystem;
                subSystemNode.Text = nodeText;
                subSystemNode.Name = nodeText;
                systemNode.Nodes.Add(subSystemNode);
            }
            var subSubSystemNode = FindNode(mapping._subSubSystem, NodeType.SubSubSystem);
            if (string.IsNullOrEmpty(subSubSystemNode.Text))
            {
                string nodeText = NodeType.SubSubSystem.ToString() + " - " + mapping._subSubSystem;
                subSubSystemNode.Text = nodeText;
                subSubSystemNode.Name = nodeText;
                subSystemNode.Nodes.Add(subSubSystemNode);
            }
        }
    }
    /// <summary>
    /// Returns an existing node from the treeview other-wise returns a new node
    /// </summary>
    /// <param name="data"></param>
    /// <param name="type"></param>
    /// <returns></returns>
    private TreeNode FindNode(string data, NodeType type)
    {
        string text = type.ToString() + " - " + data;
        if (treeView1.Nodes.Find(text, true).FirstOrDefault() != null)
        {
            return treeView1.Nodes.Find(text, true).FirstOrDefault();
        }
        else
        {
            return new TreeNode();
        }
    }
    /// <summary>
    /// Class for Mapping
    /// </summary>
    public class Mapping
    {
        public string _system;
        public string _subSystem;
        public string _subSubSystem;
    }
    /// <summary>
    /// Type of Node
    /// </summary>
    public enum NodeType
    {
        System = 0,
        SubSystem = 1,
        SubSubSystem = 2
    }