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POWhy does my Inject method not inject data to the stream?
 

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  1. POWhy does my Inject method not inject data to the stream?
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    <p>I've written a wrapper class for C# <code>Stream</code> because I want it to be able to inject data to the stream and call a function whenever data is read via ReadAsync(). However the "inject" part does not work and I have no idea why.</p> <pre><code>class ExtendedStream : Stream { private readonly Stream _originalStream; private readonly Action&lt;byte[]&gt; _readCallback; private ManualResetEvent dataInjected = new ManualResetEvent(false); private List&lt;byte&gt; data = new List&lt;byte&gt;(); private int pos = 0; public ExtendedStream(Stream originalStream, Action&lt;byte[]&gt; readCallback) { _originalStream = originalStream; _readCallback = readCallback; } public override async Task&lt;int&gt; ReadAsync(byte[] buffer, int offset, int count, System.Threading.CancellationToken cancellationToken) { var read = await _originalStream.ReadAsync(buffer, offset, count, cancellationToken); _readCallback(buffer); return read; } public void Inject(string text) { data.AddRange(new UTF8Encoding(false).GetBytes(text)); dataInjected.Set(); } private IEnumerable&lt;byte&gt; GetBytes(int count) { int returned = 0; while (returned == 0) { if (pos &lt; data.Count) { while (pos &lt; data.Count &amp;&amp; returned &lt; count) { yield return data[pos]; pos += 1; returned += 1; } } else { dataInjected.Reset(); dataInjected.WaitOne(); } } } public override int Read(byte[] buffer, int offset, int count) { var bytes = GetBytes(count).ToArray(); for (int i = 0; offset + i &lt; buffer.Length &amp;&amp; i &lt; bytes.Length; i++) { buffer[offset + i] = bytes[i]; } return bytes.Length; } public override void Write(byte[] buffer, int offset, int count) { _originalStream.Write(buffer, offset, count); } public override bool CanRead { get { return _originalStream.CanRead; } } public override bool CanSeek { get { return _originalStream.CanSeek; } } public override bool CanWrite { get { return _originalStream.CanWrite; } } public override void Flush() { _originalStream.Flush(); } public override long Length { get { return _originalStream.Length; } } public override long Position { get { return _originalStream.Position; } set { _originalStream.Position = value; } } public override long Seek(long offset, SeekOrigin origin) { return _originalStream.Seek(offset, origin); } public override void SetLength(long value) { _originalStream.SetLength(value); } } </code></pre> <p>Then I am reading the stream with XmlReader like follows.</p> <pre><code>using (XmlReader xmlReader = XmlReader.Create(_extendedStream, new XmlReaderSettings() { Async = true })) { while (await xmlReader.ReadAsync()) { switch (xmlReader.NodeType) { case XmlNodeType.EndElement: if (xmlReader.LocalName.Equals("test")) { _log.Debug("&lt;/test&gt; injected!"); } break; default: break; } } </code></pre> <p>The data is never injected if I call <code>_extendedStream.Inject("&lt;/test&gt;")</code>. Does anyone know why?</p>
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    1. USTony Stark
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    1. COYour `ReadAsync` method delegates to `_originalStream.ReadAsync`, so I don't think your overridden `Read` method (where the injection magic happens) ever gets invoked in your sample code. Have you tried stepping through with a debugger?
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      1. POWhy does my Inject method not inject data to the stream?
      1. USSteve Ruble
    2. COMhm... yes I did go through the code with the debugger. I was of the opinion (don't ask me why) that `ReadAsync` uses `Read` like suggested in the example at http://stackoverflow.com/questions/12015279/disposing-of-xmlreader-with-pending-async-read. How do I override `ReadAsync` (an example would be super)?
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      1. POWhy does my Inject method not inject data to the stream?
      1. USTony Stark
 

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