C#: This snippet is used to search through a directory and build a treeview list of nodes

Loop Through Directories Building Tree | .cs

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

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        public static List<string> formats = new List<string>();

        public Form1()
        {
            InitializeComponent();

            //add userfolder
            List<string> Directories = new List<string>();
            Directories.Add(System.Environment.GetEnvironmentVariable("USERPROFILE"));

            // get formats accepted
            formats.Add(".txt");
            formats.Add(".png");

            PopulateTree(Directories, formats);
        }

        static bool IsValidFileFormat(string filename, List<string> formats)
        {
            if (formats.Count == 0) return true;

            string ext = Path.GetExtension(filename);
            bool results = formats.Any(fileType => fileType.Equals(ext, StringComparison.OrdinalIgnoreCase));
            return results;
        }

        public static TreeNode CreateDirectoryNode(DirectoryInfo directoryInfo)
        {
            TreeNode directoryNode = new TreeNode(directoryInfo.Name);

            foreach (var directory in directoryInfo.GetDirectories())
            {
                try
                {
                    directoryNode.Nodes.Add(CreateDirectoryNode(directory));
                }
                catch (UnauthorizedAccessException) { }
            }
            foreach (var file in directoryInfo.GetFiles())
            {
                if (IsValidFileFormat(file.FullName, formats))
                {
                    TreeNode node = new TreeNode(file.FullName);
                    node.ForeColor = Color.Red;
                    directoryNode.Nodes.Add(node);
                }
            }

            return directoryNode;
        }

        public void PopulateTree(List<string> directories, List<string> formats)
        {
            // main collection of nodes which are used to populate treeview
            List<TreeNode> treeNodes = new List<TreeNode>();

            foreach (string directoryPath in directories)
            {
                if (Directory.Exists(directoryPath))
                {
                    DirectoryInfo directoryInfo = new DirectoryInfo(directoryPath);
                    treeNodes.Add(CreateDirectoryNode(directoryInfo));
                }
            }
            treeView1.Nodes.AddRange(treeNodes.ToArray());
        }
    }
}