Asp.net验证网络文件地址是否有效的方法

public static bool CheckFileURLValidity(string URL)
{
            bool IsValid = false;

            if (URL.Trim() != "" && URL.Trim().Contains("."))
            {
                try
                {
                    Uri uri = new Uri(URL);
                    HttpWebRequest webRequest = HttpWebRequest.Create(uri) as HttpWebRequest;
                    webRequest.Method = "HEAD";

                    HttpWebResponse webResponse = webRequest.GetResponse() as HttpWebResponse;
                    if (webResponse.StatusCode == HttpStatusCode.OK)
                    {
                        IsValid = true;
                    }
                }
                catch (WebException ex)
                {
                    try
                    {
                        IsValid = ((ex.Response as HttpWebResponse).StatusCode != HttpStatusCode.NotFound);
                    }
                    catch
                    {
                        IsValid = (ex.Status == WebExceptionStatus.Success);
                    }
                }
                catch (Exception ex)
                {

                }
            }

            return IsValid;
}

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