protected static string GetMimeType(string filename) {
var ext = Path.GetExtension(filename)?.ToLower();
if (ext != null) {
var regKey = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(ext);
if (regKey?.GetValue("Content Type") != null) {
return regKey.GetValue("Content Type").ToString();
}
}
return @"application/unknown";
}