Question

好的，我又来了。我需要从我正在尝试开发的C＃客户端使用Web服务。我正在使用HttpClient（来自.NET 4.5）但我正在使用 .NET 4 ，我从NuGet获得了这些Http包。除了两件事之外，我对WS一无所知：它做了什么（接收一个人的国家身份证号码并以xml格式返回他/她的一些信息），以及服务器要求使用它的凭证。

所以我的功能看起来像这样：

protected void rutBTN_Click(object sender, EventArgs e) //This void function triggers when the user clicks the button 
    {                                                   //aside the textbox where they're meant to input the ID number.
        if (rutTB.Text != "")                           //"rutTB" is the textbox aside the button
        {
            HttpClient client = new HttpClient();                       //Here i'm creating an instance of an HTTP client
            var byteArray = Encoding.ASCII.GetBytes("user:pass123"); //Load credentials into a byte array (obviously censored since that's where the actual credentials go
            client.BaseAddress = new Uri("http://wschsol.mideplan.cl"); //Base address of the web-service
            var par = "mod_perl/xml/fps-by-rut?rut=" + rutTB.Text;      //Creating a variable that holds the rest of the WS's URL
            client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Basic", Convert.ToBase64String(byteArray)); //Server authentication header with the byte array turned into a string
            client.GetAsync(par).ContinueWith(                          //Sending the GET request to the WS
                (requestTask) =>
                    {
                        HttpResponseMessage resp = requestTask.Result;  //This task receives the WS's http response and assigns it to a HttpResponseMessage variable
                        try
                        {
                            resp.EnsureSuccessStatusCode();             //This line is to check that the response was successful or else throw an exception
                            XmlDocument xmlResp = new XmlDocument();    //Creating an instance of an xml document
                            requestTask.Result.Content.ReadAsStreamAsync().ContinueWith(
                            (streamTask) =>
                            {
                                xmlResp.Load(streamTask.Result);                         //Loading the result stream into an XmlDocument object
                                xmlResp.GetEnumerator();                                 //Not really sure if this is needed.
                                XmlNodeList xmlLst = xmlResp.GetElementsByTagName("dv"); //Loading a list of xml nodes with the elements from the xml object of the type "dv"
                            });
                        }
                        catch (Exception ex)
                        {
                            throw new Exception(ex.Message, ex.InnerException);
                        } 
                    });
            testLBL.Text = "Got here";             //This is to know if the execution reached this point, and it did.
            testLBL.Visible = true;
            dvLBL.Text = xmlLst.Item(0).InnerText; //HERE is the problem. VS tells me that the "xmlLst" name doesn't exist on the current context
            dvLBL.Visible = true;                  //This label was meant to show the value of the 0 indexed item from the list. 
        }
        else
        {
            testLBL.Text = "You must enter an RUT number"; // Error label
            testLBL.Visible = true;
        }
    }

问题是，当我尝试从xmldocument对象获取数据时，它就像它不存在;或者更确切地说，只有当执行进入streamTask时才存在。我不知道如何处理这个问题。到现在为止，我只想从web服务的响应中获得ONE标签中的一个值，以便显示在我在文本框下的aspx页面上的标签上，只是为了知道我走的是正确的方式，然后才进入xml解析东西;但它不起作用。

我还尝试放置最后4条指令（那些为标签赋值并使它们可见的指令）在streamTask中，当我这样做时，它们检索数据并将其分配给元素，但我可以只有在使用断点进行调试时才会看到它，它不会显示在浏览器的页面上。

请您提前感谢你们给予我的帮助。

P.S。：以防它可能有用，这是我的故事（关于同一主题的问题之前的问题）Can't assign an http response content into an xml document on C#。

Answer 1

将XmlNodeList xmlLst声明移到任务之外。 client.GetAsync对它自己的范围进行操作，因此当你尝试访问外部的xmlLst时会得到异常。所以你新代码应该是这样的：

HttpClient client = new HttpClient();
XmlNodeList xmlLst;

然后在GetAsync()

内

xmlLst = xmlResp.GetElementsByTagName("dv");

这应该这样做。

无法使用从任务外部的任务中加载的XmlNodeList

1 个答案: