Getting null when reading extended tags on a TIF file.

Question

string tag = GetExtendedFileAttribute(@"file path goes here", "Tags");
public static string GetExtendedFileAttribute(string filePath, string propertyName)
{
string retValue = null;
Type shellAppType = Type.GetTypeFromProgID("Shell.Application");
object shell = Activator.CreateInstance(shellAppType);
Shell32.Folder folder = (Shell32.Folder)shellAppType.InvokeMember("NameSpace", System.Reflection.BindingFlags.InvokeMethod, null, shell, new object[] { @"C:\Windows\System32" });
int? foundIdx = null;
for (int i = 0; i < short.MaxValue; i++)
{
string header = folder.GetDetailsOf(null, i);
Console.WriteLine(header);
if (header == propertyName)
{
foundIdx = i;
break;
}
}
if (foundIdx.HasValue)
{
foreach (FolderItem2 item in folder.Items())
{
if (item.Name.ToUpper() == System.IO.Path.GetFileName(filePath).ToUpper())
{
retValue = folder.GetDetailsOf(item, foundIdx.GetValueOrDefault());
break;
}
}
}
return retValue;
}