Windows 8 phone检查URL是否有效，没有定义

Question

我想检查一下用户给出的URL是否有效。因为如果不是，例如"http://www.stackoverflow"，那么稍后它将使程序崩溃。我试图使用Web响应，但它找不到Irequest.GetResponse()的定义;

 try
            {
                string url = HomepageTextBox.Text;
                if (url != "")
                {
                    WebRequest Irequest = WebRequest.Create(url);
                    WebResponse Iresponse = Irequest.GetResponse();
                    if (Iresponse != null)
                    {
                    }
                }
                else
                {
                    HomepageTextBox.Text = "http://www.google.com";
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("Invalid URL");
            }

提前谢谢你:)

如果你需要更多的细节，请评论，我很乐意解释更多的细节:)

Answer 1

我记得有同样的问题，在看了MSDN网页后，我决定这是不正确的。在WP8.0中没有GetResponse()，但是在WP8.1中有GetResponseAsync()。

所以我决定使用HttpWebRequest而不是使用BeginGetResponse/EndGetResponse——据我所知，你必须使用回调。下面是一个简单的例子。

---

public void GetWebAddress(string web_address)
{
    HttpWebRequest request = (HttpWebRequest) HttpWebRequest.Create(web_address);
    if (request != null) request.BeginGetResponse(MyHttpCallback, request);            
}
void MyHttpCallback(IAsyncResult result)
{
    HttpWebRequest request = result.AsyncState as HttpWebRequest;
    if (request != null)
    {
        try
        {
            // if you're using 8.1 try enclosing theses lines with "using"
            // there is no .Close()
            WebResponse response = request.EndGetResponse(result);
            StreamReader reader;
            reader = new StreamReader(response.GetResponseStream());
            string responseText = reader.ReadToEnd();
            // reponseText now contains the html/text of the page

            reader.Close();
            response.Close();
        }
        catch (WebException e)
        {
            // your errors are here, set your flags
            string error_string = e.Message;
        }
    }
}