在上下文中找不到某些单词,缺少参考,大脑即将爆炸？

Question

我正在尝试学习C#/ Silverlight/Windows Phone 7.这里发生了什么:当我尝试直接使用MS的MSDN站点上的示例时,我遇到了各种错误:

例如:

using System;
using System.IO;
using System.Collections.Generic;
using System.Device.Location;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using Microsoft.Phone.Controls;
using Microsoft.Phone.Tasks;
using System.Device.Location;
using Microsoft.Phone.Reactive;

  private void registerPhone(object sender, RoutedEventArgs e)
    {

        // Create a request using a URL that can receive a post. 
        WebRequest request = WebRequest.Create("http://www.contoso.com/PostAccepter.aspx ");
        // Set the Method property of the request to POST.
        request.Method = "POST";
        // Create POST data and convert it to a byte array.
        string postData = "This is a test that posts this string to a Web server.";
        byte[] byteArray = Encoding.UTF8.GetBytes(postData);
        // Set the ContentType property of the WebRequest.
        request.ContentType = "application/x-www-form-urlencoded";
        // Set the ContentLength property of the WebRequest.
        request.ContentLength = byteArray.Length;
        // Get the request stream.
        Stream dataStream = request.GetRequestStream();
        // Write the data to the request stream.
        dataStream.Write(byteArray, 0, byteArray.Length);
        // Close the Stream object.
        dataStream.Close();
        // Get the response.
        WebResponse response = request.GetResponse();
        // Display the status.
        Console.WriteLine(((HttpWebResponse)response).StatusDescription);
        // Get the stream containing content returned by the server.
        dataStream = response.GetResponseStream();
        // Open the stream using a StreamReader for easy access.
        StreamReader reader = new StreamReader(dataStream);
        // Read the content.
        string responseFromServer = reader.ReadToEnd();
        // Display the content.
        Console.WriteLine(responseFromServer);
        // Clean up the streams.
        reader.Close();
        dataStream.Close();
        response.Close();

    }

它告诉我

1) The name 'Encoding' does not exist in this context

2) System.Net.WebRequest does not contain a definition for GetStreamRequest and no extension method GetRequestStream accepting a first argument of type System.Net.WebRequest could be found (are you missing a using directive... etc

3)ContentLength的类似消息

4)GetResponse的类似消息

我不知道我需要什么库"使用",即使我认为我"正在使用"正确的库,它也会给我带来错误.我究竟做错了什么？

Answer 1

本Encoding类驻留在System.Text命名空间.你必须将它添加到"使用".

至于其他消息,这与Silverlight的局限性有关.我认为,MSDN样本取自.NET Framework的"大"版本,不是吗？

在Silverlight中,您会看到,为了防止不良应用程序行为(例如阻止调用),某些内容是不允许的,并且由于资源限制,某些内容不受支持.

特别ContentLength是后者之一.库将根据您写入请求的实际数据量确定内容长度.只需删除该行,您就可以了.

但GetResponseStream()实际上是前者之一.这与此操作意味着实际打开网络连接这一事实有关,这可能需要一段时间.由于Silverlight中不允许阻塞调用,因此该GetResponseStream()方法也必须使用.

相反,你应该使用所谓的"异步模式" - 即一对方法BeginGetResponseStream/ EndGetResponseStream.您可以通过调用Begin方法并提供将在操作完成后调用的回调来执行此操作.然后,在该回调中,您使用该End方法来获取操作的结果.像这样:

            request.BeginGetRequestStream( ar =>
            {
                var dataStream = request.EndGetRequestStream( ar );

                // Write the data to the request stream.
                dataStream.Write( byteArray, 0, byteArray.Length );
                // Close the Stream object.
                dataStream.Close();

                // and so on...

            }, null );

该GetResponse方法也是如此.