Собственный TreeView и TreeNode для отображения файлов и папок с их системными иконками

public partial class WinTreeView: TreeView
    {
        [DllImport("uxtheme.dll", ExactSpelling = true, CharSet = CharSet.Unicode)]
        private static extern int SetWindowTheme(IntPtr hwnd, string pszSubAppName, string pszSubIdList);
 
        public WinTreeView()
        {
            SetWindowTheme(this.Handle, "explorer", null);
        }
    }
 
public partial class PathTreeNode : TreeNode
    {
        private string fnPath = "";
 
        public PathTreeNode(string text, string fnPath) : base(text)
        {
            this.fnPath = fnPath;
        }
 
        public string FnPath { get => fnPath; set => fnPath = value; }
 
        public bool IsFile()
        {
            return File.Exists(fnPath);
        }
 
        public bool IsDirectory()
        {
            return !File.Exists(fnPath) && Directory.Exists(fnPath);
        }
    }

public List<PathTreeNode> ExtractAssociatedIconEx(string startDir, TreeView tree)
{
    List<PathTreeNode> resultList = new List<PathTreeNode>();
    ImageList imageList1 = new ImageList();
 
    System.IO.DirectoryInfo dir = new System.IO.DirectoryInfo(startDir);
 
    PathTreeNode item;
 
    foreach (System.IO.FileInfo file in dir.GetFiles())
    {
        // Set a default icon for the file.
        Icon iconForFile = SystemIcons.WinLogo;
 
        item = new PathTreeNode(file.Name, file.FillName);
 
        if (!imageList1.Images.ContainsKey(file.Extension))
        {
            iconForFile = System.Drawing.Icon.ExtractAssociatedIcon(file.FullName);
            imageList1.Images.Add(file.Extension, iconForFile);
        }
        item.ImageKey = file.Extension;
        resultList.Add(item);
    }
    tree.ImageList = imageList1;
    return resultList;
}
 
public class PathTreeNode : TreeNode
    {
        private string fnPath = "";
        private bool _isFile;
 
        public PathTreeNode(string text, string fnPath) : base(text)
        {
            this.fnPath = fnPath;
            _isFile = File.Exists(fnPath);
        }
 
        public string FnPath { get => fnPath; set => fnPath = value; }
 
        public bool IsFile() { get => _isFile; }
    }

private async void RefreshListProject()
        {
            treeViewRMProjects.Nodes.Clear();
            await Task.Delay(10);
 
            if (Settings.RPGMakers.Count <= 0) return;
            if (this.Settings.SelectTab < 0) return;
 
            if (this.Settings.RPGMakers[this.Settings.SelectTab].PathsProjects.Count <= 0 &&
                this.Settings.RPGMakers[this.Settings.SelectTab].Projects.Count <= 0) return;
 
            var ListAllProjects = this.Settings.RPGMakers[this.Settings.SelectTab].AllDirProjects;
 
            if (ListAllProjects.Count <= 0) return;
 
            foreach (var item in ListAllProjects.Select((e, i) => new { Value = e, Index = i }))
            {
                TreeNode tds = treeViewRMProjects.Nodes.Add(item.Value.Name);
                tds.Tag = item.Value.Path;
                LoadSubDirectories(item.Value.Path, tds);
                LoadFiles(item.Value.Path, tds);
            }
 
            void LoadSubDirectories(string dir, TreeNode td)
            {
                string[] subdirectoryEntries = Directory.GetDirectories(dir);
                // Loop through them to see if they have any other subdirectories
                foreach (string subdirectory in subdirectoryEntries)
                {
                    DirectoryInfo di = new DirectoryInfo(subdirectory);
                    TreeNode tds = td.Nodes.Add(di.Name);
                    tds.Tag = di.FullName;
                    LoadSubDirectories(subdirectory, tds);
                    LoadFiles(subdirectory, tds);
                }
            }
 
            void LoadFiles(string dir, TreeNode td)
            {
                string[] Files = Directory.GetFiles(dir, "*.*");
                // Loop through them to see files
                foreach (string file in Files)
                {
                    FileInfo fi = new FileInfo(file);
                    TreeNode tds = td.Nodes.Add(fi.Name);
                    tds.Tag = fi.FullName;
                }
            }
        }

void LoadSubDirectories(string dir, PathTreeNode td)
{
   string[] subdirectoryEntries = Directory.GetDirectories(dir);
   // Loop through them to see if they have any other subdirectories
   foreach (string subdirectory in subdirectoryEntries)
   {
      DirectoryInfo di = new DirectoryInfo(subdirectory);
      PathTreeNode tds = new PathTreeNode(di.Name, di.FullName);
      td.Nodes.Add(tds);
      LoadSubDirectories(subdirectory, tds);
      LoadFiles(subdirectory, tds);
   }
}
 
void LoadFiles(string dir, PathTreeNode td)
{
   string[] Files = Directory.GetFiles(dir, "*.*");
   // Loop through them to see files
   foreach (string file in Files)
   {
      FileInfo fi = new FileInfo(file);
      PathTreeNode tds = new PathTreeNode(fi.Name, fi.FullName);
      td.Nodes.Add(tds);
    }
}

double x = 1234.7;
int a = (int)x;

void LoadSubDirectories(string dir, PathTreeNode td)
            {
                string[] subdirectoryEntries = Directory.GetDirectories(dir);
                // Loop through them to see if they have any other subdirectories
                foreach (string subdirectory in subdirectoryEntries)
                {
                    DirectoryInfo di = new DirectoryInfo(subdirectory);
                    PathTreeNode tdsDir = new PathTreeNode(di.Name, di.FullName);
                    tdsDir.ImageKey = "explorer_Dir.png";
                    LoadFiles(subdirectory, tdsDir);
                    LoadSubDirectories(subdirectory, tdsDir);
                    td.Nodes.Add(tdsDir);
                }
            }
 
            void LoadFiles(string dir, PathTreeNode td)
            {
                string[] Files = Directory.GetFiles(dir, "*.*");
                // Loop through them to see files
                foreach (string file in Files)
                {
                    FileInfo fi = new FileInfo(file);
                    PathTreeNode tdsF = new PathTreeNode(fi.Name, fi.FullName);
                    if (!imageListRMProjects.Images.ContainsKey(fi.Extension))
                    {
                        var iconForFile = System.Drawing.Icon.ExtractAssociatedIcon(fi.FullName);
                        imageListRMProjects.Images.Add(fi.Extension, iconForFile);
                    }
                    tdsF.ImageKey = fi.Extension;
                    td.Nodes.Add(tdsF);
                }
            }
 
            foreach (var item in ListAllProjects.Select((e, i) => new { Value = e, Index = i }))
            {
                PathTreeNode tds = new PathTreeNode(item.Value.Name, item.Value.Path);
                tds.ImageKey = "explorer_Dir.png";
                LoadFiles(item.Value.Path, tds);
                LoadSubDirectories(item.Value.Path, tds);
                treeViewRMProjects.Nodes.Add(item.Value.Name);
            }
        }

TreeNode node = new PathTreeNode();
PathTreeNode pathNode = (PathTreeNode)node;