c# - 为什么这个异常声称代码不写数据？

Question

如果您运行此代码，它将抛出 WebException。内部异常是“无法为不写入数据的操作设置 Content-Length 或 Chunked Encoding”。我不明白问题的本质。谁能给这个黑暗的角落投光？

using System.Diagnostics;
using System.Net;
using System.Text;

namespace sandpit
{
  static class Program
  {
    static void Main()
    {
      string INITIAL_URI = "http://docs.live.net/SkyDocsService.svc";
      string SOAP = "<s:Envelope xmlns:s=\"http://schemas.xmlsoap.org/soap/envelope/\"><s:Body><GetWebAccountInfoRequest xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns=\"http://schemas.microsoft.com/clouddocuments\"><BaseRequest><ClientAppId>SkyDrive Service Client</ClientAppId><Market>en-US</Market><SkyDocsServiceVersion>v1.0</SkyDocsServiceVersion></BaseRequest><GetReadWriteLibrariesOnly>false</GetReadWriteLibrariesOnly></GetWebAccountInfoRequest></s:Body></s:Envelope>";
      using (WebClient wc = new WebClient())
      {
        wc.Encoding = Encoding.UTF8;
        wc.Headers["SOAPAction"] = "GetWebAccountInfo";
        wc.Headers["Accept-Language"] = "en-US";
        wc.Headers["Accept"] = "text/xml";
        wc.Headers["Content-Type"] = "text/xml; charset=utf-8";
        string response = wc.UploadString(INITIAL_URI, SOAP);
        Debug.WriteLine(response);
      }
    }
  }
}

Answer 1

问题是由网络服务器重定向造成的。

不幸的是，您必须将 WebClient 子类化才能解决此问题。这比看起来更难，因为 Silverlight(任何风格)不喜欢这样并抛出与继承相关的异常，直到您猜测需要重写构造函数并将其归因于 SecurityCritical。

public class WebClient2 : WebClient
{
  [SecurityCritical]
  public WebClient2() : base() { }  
  protected override WebRequest GetWebRequest(System.Uri address)
  {
    var wr = base.GetWebRequest(address);
    if (wr is HttpWebRequest)
      (wr as HttpWebRequest).AllowAutoRedirect = false;
    return wr;
  }
}

如果您想更进一步，您可以在 WebClient2 上显示一个 AllowAutoRedirect 属性并将其全部连接起来。