检测URL地址是否有响应

/// <summary>
/// 检测URL地址是否可以访问
/// </summary>
/// <param name="Url">URL地址(以http://开头)</param>
/// <returns>返回OK</returns>
/// <example>IsUrlVist("http://www.baidu.com")</example>
public static string IsUrlVisit(string Url)
{
string reVlue = null;
try
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(new Uri(Url));
request.Timeout = 30;      //超时时间
ServicePointManager.Expect100Continue = false;
((HttpWebResponse)request.GetResponse()).Close();
reVlue = "OK";
}
catch (WebException ex)
{
reVlue = ex.ToString();
}
return reVlue;
}