c# using + XmlWriter.Create = "Cannot access a closed Stream."
c#, silverlight, using, xmlwriter
Solution
Can you give us the complete stack trace of the exception? My first guess is that the `XmlWriter` still tries to access the stream within the `Dispose()` method of the `XmlWriter`.
In your second and fourth code example you place the `StreamReader` in a using-block. This causes the invocation of the `Dispose()` method of the `StreamReader` at the end of this block. This method closes both the reader and the underlying stream. After this, the `Dispose()` method of the `XmlWriter` can't access the stream anymore.
Update: Based on the stackstrace it seems I was right. The `Dispose()` method invokes `Close()`, which in turn wants to flush an already closed stream. This looks like a bug since there should be nothing left to flush.
You already gave the solution: don't close the memorystream before the XmlWriter disposes.
(I assume you know that a using-block implicitly disposes the used object, and that disposing a `StreamReader` or `StreamWriter` implicitly disposes (and closes) the underlying stream.)
Problem
Why this works: ``` 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(); } } } ``` but this does not work ("Cannot access a closed Stream."): Only difference is `var dummy = XmlWriter.Create(ms)` instead of `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(); } } } ``` Stack trace: ``` 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: ``` Also this does not work (same error): ``` 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(); } } } ``` Stack trace: ``` 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: ``` but this works (only difference is `StreamReader` w/o `using`): ``` 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(); } } ```