FIX: The XmlTextReader class constructor never returns and appears to stop responding in the .NET Framework 1.1 with Service Pack 1 (885456)

SYMPTOMS

Consider the following scenario. In the Microsoft .NET Framework 1.1 with Service Pack 1 (SP1), you use the XmlTextReader class, and you pass a stream as an argument to the XmlTextReader class constructor. When you do this, the XmlTextReader class constructor never returns. Additionally, the XmlTextReader class constructor appears to stop responding.

This problem only occurs when you use streams that block on the Read method. For example, this problem occurs when you use the System.Net.Sockets.NetworkStream class.

Note You do not experience this problem in the .NET Framework 1.1.

CAUSE

This problem occurs because the XmlTextReader class continues to call the System.IO.Stream.Read method until one of the following conditions is true:

The total amount of data that the Read method returns equals 4 KB.
The Read method returns 0. This return value indicates that the end of file (EOF) is reached.

The System.Net.Sockets.NetworkStream class blocks until more data arrives. The XmlTextReader class will not return control until the underlying call to the System.IO.Stream.Read method returns a total of 4 KB of data.

RESOLUTION

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next .NET Framework 1.1 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

   Date         Time   Version        Size       File name
   ------------------------------------------------------------
   01-Aug-2005  20:14  1.1.4322.2340  1,355,776  System.xml.dll

MORE INFORMATION

Steps to reproduce the problem

Start Microsoft Visual Studio .NET 2003 on a computer that has the .NET Framework 1.1 with SP1 installed.
On the File menu, click New, and then click Project.
Under Project Type, click Visual C# Projects.
Under Template, click Console Application.
In the Name box, type ApplicationName, and then click OK.
In Solution Explorer, right-click Class1.cs, and then click View Code.

In the code window, replace all the generated code with the following code.

using System;
using System.IO; 
using System.Net; 
using System.Net.Sockets; 
using System.Xml; 

namespace TextReaderBlock
{
	class Class1
	{
		[STAThread]
		static void Main(string[] args)
		{
			TcpListener server; 
			TcpClient client; 
			StreamWriter sw;
			Stream clientStream;
			Stream serverStream;
			XmlTextReader reader;

			int port = 12345; 
			string ip = "127.0.0.1";

			server = new TcpListener( IPAddress.Parse(ip), port ); 
			server.Start(); 
			client = new TcpClient( ip, port ); 
			clientStream = client.GetStream(); 

			string xml = "<?xml version=\"1.0\"?>\r\n<root>value</root>";

			sw = new StreamWriter(clientStream);
			sw.Write(xml);
			sw.Flush();
			clientStream.Flush(); 
			//Uncomment the next line to close the stream and allow the constructor to return.
			//This could be used as a workaround sometimes.
			//clientStream.Close();

			client = server.AcceptTcpClient(); 
			serverStream = client.GetStream(); 

			//The next line blocks if the amount of data in the stream is less than 4 KB
			//and the underlying stream blocks on Read().
			//The hotfix addresses this blocking behavior.
			reader = new XmlTextReader( serverStream ); 
			while (reader.Read()) 
			{
				bool eom = false; 
				while (!eom && reader.Read()) 

				{ 
				//Process nodes 
				switch( reader.NodeType ) 
				{ 
				// All the other nodes would be decoded here. 
				// Decode EndElement 
				case XmlNodeType.EndElement: 
					eom = true; 
					break; 
				} 
				}

			}
			Console.WriteLine("End of reading"); 
		}
	}
}

On the Debug menu, click Start.

Note When the following line of code is commented, you do not receive the "End of reading" output, and the code appears to stop responding.

clientStream.Close()

When this line of code is not commented, you receive the "End of reading" output.

For more information, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates