为什么在尝试更新 OData 服务时 HttpWebRequest.GetResponse() 会挂起？

我正在用 C# 编写一个 OData 消费者。我可以成功删除一个条目，但由于某种原因，当我尝试更新时，它只是挂起/冻结在 GetResponse() 上。它甚至忽略了我的超时。下面是我的测试代码。有什么明智的建议吗？

XDocument doc = XDocument.Parse(
@"<?xml version=""1.0"" encoding=""iso-8859-1"" standalone=""yes""?>
<entry xml:base=""http://localhost/odata/service.svc/"" xmlns:d=""http://schemas.microsoft.com/ado/2007/08/dataservices"" xmlns:m=""http://schemas.microsoft.com/ado/2007/08/dataservices/metadata"" xmlns=""http://www.w3.org/2005/Atom"">
  <id>http://localhost/odata/service.svc/SimpleTests(7)</id>
  <title type=""text""></title>
  <updated>2011-07-18T12:19:43Z</updated>
  <author>
    <name />
  </author>
  <link rel=""edit"" title=""SimpleTest"" href=""SimpleTests(7)"" />
  <category term=""MetastormModel.SimpleTest"" scheme=""http://schemas.microsoft.com/ado/2007/08/dataservices/scheme"" />
  <content type=""application/xml"">
    <m:properties>
      <d:ID m:type=""Edm.Int32"">7</d:ID>
      <d:varcharcol>EFGH</d:varcharcol>
      <d:intcol m:type=""Edm.Int32"">-44</d:intcol>
      <d:realcol m:type=""Edm.Single"">22.11</d:realcol>
      <d:datetimecol m:type=""Edm.DateTime"">1999-12-31T00:00:00</d:datetimecol>
      <d:imagecol m:type=""Edm.Binary"" m:null=""true"" />
      <d:moneycol m:type=""Edm.Decimal"">1000000.0000</d:moneycol>
      <d:textcol>WOW!</d:textcol>
    </m:properties>
  </content>
</entry>");

HttpWebRequest request =
 (HttpWebRequest)HttpWebRequest.Create("http://localhost/odata/service.svc/SimpleTests(7)");
request.Method = "PUT";
request.Accept = "application/atom+xml";
request.Timeout = 1000;
request.ContentType = "application/atom+xml;type=entry";
using (var writer = XmlWriter.Create(request.GetRequestStream()))
{
    doc.WriteTo(writer);
    writer.Close();
}
using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
{
}

在摆弄 Fiddler 之后，我想出了以下可行的解决方案。似乎解决问题的部分是指定 request.ContentLength。我不知道有更简单的方法来获取长度，所以如果您知道的话，请随时发表评论。

XDocument doc = XDocument.Parse(
@"<?xml version=""1.0"" encoding=""utf-8"" standalone=""yes""?>
<entry xmlns:d=""http://schemas.microsoft.com/ado/2007/08/dataservices"" xmlns:m=""http://schemas.microsoft.com/ado/2007/08/dataservices/metadata"" xmlns=""http://www.w3.org/2005/Atom"">
  <category scheme=""http://schemas.microsoft.com/ado/2007/08/dataservices/scheme"" term=""MetastormModel.SimpleTest"" />
  <title />
  <author>
    <name />
  </author>
  <updated>2011-07-19T09:28:03.173654Z</updated>
  <id>http://localhost/odata/service.svc/SimpleTests(7)</id>
  <content type=""application/xml"">
    <m:properties>
      <d:ID m:type=""Edm.Int32"">7</d:ID>
      <d:datetimecol m:type=""Edm.DateTime"">1950-01-01T00:00:00</d:datetimecol>
      <d:imagecol m:type=""Edm.Binary"" m:null=""true"" />
      <d:intcol m:type=""Edm.Int32"">-44</d:intcol>
      <d:moneycol m:type=""Edm.Decimal"">12345.0000</d:moneycol>
      <d:realcol m:type=""Edm.Single"">22.11</d:realcol>
      <d:textcol>Hello There</d:textcol>
      <d:varcharcol>EFGH</d:varcharcol>
    </m:properties>
  </content>
</entry>");

HttpWebRequest request =
 (HttpWebRequest)HttpWebRequest.Create("http://localhost/odata/service.svc/SimpleTests(7)");
request.Method = "MERGE";
request.Accept = "application/atom+xml,application/xml";
request.Timeout = 20000;
request.ContentType = "application/atom+xml";
using (MemoryStream stream = new MemoryStream())
{
    using (var writer = XmlWriter.Create(stream))
    {
        doc.WriteTo(writer);
        writer.Close();
    }
    request.ContentLength = stream.Length;
    using (var writer = XmlWriter.Create(request.GetRequestStream()))
    {
        doc.WriteTo(writer);
        writer.Close();
    }
}