FileNameToFileTypeConverter WPF

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Security;
using System.Text;
using System.Windows.Data;

namespace Core.UI.Converters
{
    public class FileNameToFileTypeConverter : IMultiValueConverter, IValueConverter
    {
        public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            if (values != null && values.Length >= 2 && values[0] is string && values[1] is string)
            {
                string title = (string)values[0];
                string extension = (string)values[1];
                return GetFileType(title, extension);
            }
            return null;
        }

        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture)
        {
            throw new NotImplementedException();
        }


        //implements IValueConverter for just extension
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            if (value == null)
                return string.Empty;

            string extension = value.ToString();
            string title = "fakefile";

            return FileNameToFileTypeConverter.GetFileType(title, extension);
        }

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

        /// <summary>
        /// Gets the windows file type associated with a file's extension
        /// </summary>
        public static string GetFileType(string title, string extension)
        {
            if (string.IsNullOrWhiteSpace(title) || string.IsNullOrWhiteSpace(extension))
                return string.Empty;

            string fileName = string.Format("{0}.{1}", title, extension);
            SafeNativeMethods.SHFILEINFO info = new SafeNativeMethods.SHFILEINFO();
            uint dwFileAttributes = SafeNativeMethods.FILE_ATTRIBUTE.FILE_ATTRIBUTE_NORMAL;
            uint uFlags = (uint)(SafeNativeMethods.SHGFI.SHGFI_TYPENAME | SafeNativeMethods.SHGFI.SHGFI_USEFILEATTRIBUTES);
            SafeNativeMethods.SHGetFileInfo(fileName, dwFileAttributes, ref info, (uint)Marshal.SizeOf(info), uFlags);
            return info.szTypeName;
        }

        [SuppressUnmanagedCodeSecurity]
        internal static class SafeNativeMethods
        {
            [StructLayout(LayoutKind.Sequential)]
            public struct SHFILEINFO
            {
                public IntPtr hIcon;
                public int iIcon;
                public uint dwAttributes;
                [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
                public string szDisplayName;
                [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 80)]
                public string szTypeName;
            };

            public static class FILE_ATTRIBUTE
            {
                public const uint FILE_ATTRIBUTE_NORMAL = 0x80;
            }

            public static class SHGFI
            {
                public const uint SHGFI_TYPENAME = 0x000000400;
                public const uint SHGFI_USEFILEATTRIBUTES = 0x000000010;
            }

            [DllImport("shell32.dll")]
            internal static extern IntPtr SHGetFileInfo(string pszPath, uint dwFileAttributes, ref SHFILEINFO psfi, uint cbSizeFileInfo, uint uFlags);
        }
    }
}