HeaderToImageConverter.cs

using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Windows.Data;
using System.Windows.Media;
using System.Windows.Media.Imaging;

namespace WpfTreeView
{
    /// <summary>
    /// Converts a full path to a specific image type of a drive, folder or file.
    /// </summary>
    
    [ValueConversion(typeof(string), typeof(BitmapImage))]
    public class HeaderToImageConverter : IValueConverter
    {
        public IDictionary<string, ImageSource> KnownFiles { get; set; }

        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            // Get the full Path
            var path = (string)value;

            // if the path is null, ignore
            if (path == null)
                return null;

            // Get the name of the file/folder
            var name = MainWindow.GetFileFolderName(path);

            // By default, we presume an image
            var image = "Images/file.png";

            // If the name is blank, we presume it's a drive as we cannot have a blank file or folder name
            if (string.IsNullOrEmpty(name))
                image = "Images/drive.png";
            else if (new FileInfo(path).Attributes.HasFlag(FileAttributes.Directory)) // checks if this path is a directory
                image = "Images/folder-closed.png";
            else if (KnownFiles != null && KnownFiles.ContainsKey(Path.GetExtension(path)))
                return KnownFiles[Path.GetExtension(path)];

            return new BitmapImage(new Uri($"pack://application:,,,/{image}"));

        }

        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            throw new NotImplementedException();
        }
    }
}