c＃using + XmlWriter.Create =＆ldquo;无法访问已关闭的流。＆rdquo;

为什么这样有效：

using (var ms = new MemoryStream())
{
    using (var dummy = new StreamWriter(ms))
    {
        var sw = new StreamWriter(ms);
        sw.WriteLine("Hello World");
        sw.Flush();
        using (StreamReader rdr = new StreamReader(ms))
        {
            ms.Position = 0;
            textBoxExc.Text = rdr.ReadToEnd();
        }
    }
}

但这不起作用（“无法访问封闭的流。”）：唯一的区别是var dummy = XmlWriter.Create(ms)而不是var dummy = new StreamWriter(ms)

using (var ms = new MemoryStream())
{
    using (var dummy = XmlWriter.Create(ms))
    {
        var sw = new StreamWriter(ms);
        sw.WriteLine("Hello World");
        sw.Flush();
        using (StreamReader rdr = new StreamReader(ms))
        {
            ms.Position = 0;
            textBoxExc.Text = rdr.ReadToEnd();
        }
    }
}

堆栈跟踪：

System.ObjectDisposedException was unhandled by user code
  Message=Cannot access a closed Stream.
  ObjectName=""
  StackTrace:
       w System.IO.__Error.StreamIsClosed()
       w System.IO.MemoryStream.Write(Byte[] buffer, Int32 offset, Int32 count)
       w System.Xml.XmlUtf8RawTextWriter.FlushBuffer()
       w System.Xml.XmlUtf8RawTextWriter.Flush()
       w System.Xml.XmlWellFormedWriter.Close()
       w System.Xml.XmlWriter.Dispose(Boolean disposing)
       w System.Xml.XmlWriter.Dispose()
       w SerializeTest.MainPage.buttonExc_Click(Object sender, RoutedEventArgs e)
       w System.Windows.Controls.Primitives.ButtonBase.OnClick()
       w System.Windows.Controls.Button.OnClick()
       w System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
       w System.Windows.Controls.Control.OnMouseLeftButtonUp(Control ctrl, EventArgs e)
       w MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName)
  InnerException:

这也行不通（同样的错误）：

using (var ms = new MemoryStream())
{
     using (var writer = XmlWriter.Create(ms))
    {
        var serializer = new DataContractSerializer(typeof(T));
        serializer.WriteObject(writer, objectToSave);
        writer.Flush();
        ms.Position = 0;
        using (StreamReader rdr = new StreamReader(ms))
        {
            return rdr.ReadToEnd();
        }
    }
}

堆栈跟踪：

System.ObjectDisposedException was unhandled by user code
  Message=Cannot access a closed Stream.
  ObjectName=""
  StackTrace:
       w System.IO.__Error.StreamIsClosed()
       w System.IO.MemoryStream.Write(Byte[] buffer, Int32 offset, Int32 count)
       w System.Xml.XmlUtf8RawTextWriter.FlushBuffer()
       w System.Xml.XmlUtf8RawTextWriter.Flush()
       w System.Xml.XmlWellFormedWriter.Close()
       w System.Xml.XmlWriter.Dispose(Boolean disposing)
       w System.Xml.XmlWriter.Dispose()
       w SerializeTest.SerializeToStringTest[T](T objectToSave)
       w SerializeTest.MainPage.button2A_Click(Object sender, RoutedEventArgs e)
       w System.Windows.Controls.Primitives.ButtonBase.OnClick()
       w System.Windows.Controls.Button.OnClick()
       w System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
       w System.Windows.Controls.Control.OnMouseLeftButtonUp(Control ctrl, EventArgs e)
       w MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName)
  InnerException:

但这很有效（唯一不同的是StreamReaderw/ousing）：

using (var ms = new MemoryStream())
{
     using (var writer = XmlWriter.Create(ms))
    {
        var serializer = new DataContractSerializer(typeof(T));
        serializer.WriteObject(writer, objectToSave);
        writer.Flush();
        ms.Position = 0;
        StreamReader rdr = new StreamReader(ms);
        return rdr.ReadToEnd();
    }
}

已邀请:

2 个回复

凄嘛姥

你能告诉我们异常的完整堆栈跟踪吗？我的第一个猜测是XmlWriter仍然试图在XmlWriter的Dispose()方法中访问流。在第二个和第四个代码示例中，将StreamReader放在一个使用块中。这导致在该块结束时调用StreamReader的Dispose()方法。此方法关闭阅读器和基础流。在此之后，XmlWriter的Dispose()方法不再能够访问流。更新：基于stackstrace看起来我是对的。 Dispose()方法调用Close()，后者又想要刷新已经关闭的流。这看起来像一个bug，因为没有什么可以冲洗。您已经提供了解决方案：在XmlWriter处理之前不要关闭内存流。（我假设您知道using-block隐式处理使用过的对象，并且处理StreamReader或StreamWriter隐式处理（并关闭）基础流。）

物崎巩

只需将MemoryStream块中的读取移到一个级别上即可。

using (var ms = new MemoryStream())
{
     using (var writer = XmlWriter.Create(ms))
    {
        var serializer = new DataContractSerializer(typeof(T));
        serializer.WriteObject(writer, objectToSave);
        writer.Flush();
        ms.Position = 0;        
    }
    using (StreamReader rdr = new StreamReader(ms))
    {
        return rdr.ReadToEnd();
    }
}

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c＃using + XmlWriter.Create =＆ldquo;无法访问已关闭的流。＆rdquo;

2 个回复

发起人

using

xmlwriter

问题状态

c＃using + XmlWriter.Create =＆ldquo;无法访问已关闭的流。＆rdquo;

与内容相关的链接

2 个回复

发起人

using

xmlwriter

问题状态