public static string GetMimeType(this File file)
{
if (file != null)
{
var extension = Path.GetExtension(file.Name);
var fileExtension = extension.IsNullOrWhiteSpace() ? file.Name : extension.ToLower();
var rk = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(fileExtension);
if (rk != null && rk.GetValue("Content Type") != null) return rk.GetValue("Content Type").ToString();
}
return "application/octet-stream";
}