如何获取现有文件的ContentType属性

 public static string GetFileContentType(string filename)
        {
            string[] array = filename.Split('.');
            string result = string.Empty;
            string suffix="."+array[array.Length-1];
            RegistryKey rg = Microsoft.Win32.Registry.ClassesRoot.OpenSubKey(suffix);
            object obj=rg.GetValue("Content Type");
            result =obj!=null?obj.ToString():string.Empty;
            rg.Close();
            return result;
        }