获取文件的ContentType

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;
}