判断网络文件是否存在

判断网络文件时，得到的HttpWebResponse要及时关闭，否则代码执行多次，会出现httprequest超时，

代码如下：

 public static bool IsExist(String url)
        {
            try
            {
              
               
                HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(url);
              
                myRequest.Timeout = 20000;
                myRequest.Method = "HEAD";
                HttpWebResponse myResponse = (HttpWebResponse)myRequest.GetResponse();
                myResponse.Close();
                if (myResponse.ContentLength == 0)//file not exist
                {
                    return false;
                }
                else
                {
                    return true;
                }
                
              

            }

            catch (Exception ex)
            {
                if (ex.Message == "The remote server returned an error: (404) Not Found.")
                    return false;
                else
                    return false;

            }

        }

黄色部分是重点，解决多次调用此方法出现请求超时。