C#过滤html中的a标签

/// <summary>
/// 过滤html中的a标签
/// </summary>
/// <param name="str"></param>
/// <returns></returns>
public static string RemoveA(string str)
{
    str = Regex.Replace(str, @"<a\s*[^>]*>", "", RegexOptions.IgnoreCase);
    str = Regex.Replace(str, @"</a>", "", RegexOptions.IgnoreCase);

    return str;
}