封装stream，在读写stream时提供事件通知_.Net教程

private Stream stream;
public EventStream(Stream stream)
{
if (stream == null) throw new ArgumentNullException("EventStream");
this.stream = stream;
}

[ ==== Stream members ==== ]#region [ ==== Stream members ==== ]
public override bool CanRead
{
get { return stream.CanRead; }
}

public override bool CanSeek
{
get { return stream.CanSeek; }
}

public override bool CanWrite
{
get { return stream.CanWrite; }
}

public override void Flush()
{
stream.Flush();
}

public override long Length
{
get { return stream.Length; }
}

public override long Position
{
get
{
return stream.Position;
}
set
{
stream.Position = value;
}
}

public override int Read(byte[] buffer, int offset, int count)
{
int readSize = stream.Read(buffer, offset, count);
if (OnBeforeRead != null)
OnBeforeRead(this, new FStreamDataEventArgs(buffer, offset, readSize));
return readSize;
}

public override long Seek(long offset, SeekOrigin origin)
{
return stream.Seek(offset, origin);
}

public override void SetLength(long value)
{
stream.SetLength(value);
}

public override void Write(byte[] buffer, int offset, int count)
{
if (OnBeforeWrite != null)
OnBeforeWrite(this, new FStreamDataEventArgs(buffer, offset, count));
stream.Write(buffer, offset, count);
}

public override IAsyncResult BeginRead(byte[] buffer, int offset, int count,
AsyncCallback callback, object state)
{
InternalAsyncState myState = new InternalAsyncState(
new FStreamDataEventArgs(buffer, offset, count), state);
AsyncCallback myCallback = new AsyncCallback(
new InternalCallback(OnBeforeRead, callback).Callback);
return new EventStreamAsyncResult(
stream.BeginRead(buffer, offset, count, myCallback, myState));
}

public override int EndRead(IAsyncResult asyncResult)
{
EventStreamAsyncResult esar = asyncResult as EventStreamAsyncResult;
if (esar != null)
return stream.EndRead(esar.InternalAsyncResult);
else
return stream.EndRead(asyncResult);
}

public override IAsyncResult BeginWrite(byte[] buffer, int offset, int count, AsyncCallback callback, object state)
{
InternalAsyncState myState = new InternalAsyncState(
new FStreamDataEventArgs(buffer, offset, count), state);
AsyncCallback myCallback = new AsyncCallback(
new InternalCallback(OnBeforeWrite, callback).Callback);
return new EventStreamAsyncResult(
stream.BeginWrite(buffer, offset, count, myCallback, myState));
}

public override void EndWrite(IAsyncResult asyncResult)
{
stream.EndWrite(asyncResult);
}

#endregion

private class InternalCallback
{
private AsyncCallback callback;
private EventHandler<FStreamDataEventArgs> internalHandler;

public InternalCallback(EventHandler<FStreamDataEventArgs> internalHandler, AsyncCallback callback)
{
this.internalHandler = internalHandler;
this.callback = callback;
}

internal void Callback(IAsyncResult asyncResult)
{
InternalAsyncState myState = asyncResult.AsyncState as InternalAsyncState;
if (internalHandler != null && myState != null)
internalHandler(this, myState.StreamDataEventArgs);
callback(new EventStreamAsyncResult(asyncResult));
}
}

private class InternalAsyncState
{
object state;
FStreamDataEventArgs streamDataEventArgs;

public object State
{
get { return state; }
}

public FStreamDataEventArgs StreamDataEventArgs
{
get { return streamDataEventArgs; }
}

public InternalAsyncState(FStreamDataEventArgs streamDataEventArgs, object state)
{
this.streamDataEventArgs = streamDataEventArgs;
this.state = state;
}
}

private class EventStreamAsyncResult : IAsyncResult
{
IAsyncResult ar;

public EventStreamAsyncResult(IAsyncResult ar)
{
if (ar == null) throw new ArgumentNullException("EventStreamAsyncResult");
this.ar = ar;
}
IAsyncResult Members#region IAsyncResult Members

public object AsyncState
{
get
{
InternalAsyncState myState = ar.AsyncState as InternalAsyncState;
if (myState != null)
return myState.State;
else
return ar.AsyncState;
}
}

internal IAsyncResult InternalAsyncResult
{
get { return ar; }
}

public System.Threading.WaitHandle AsyncWaitHandle
{
get { return ar.AsyncWaitHandle; }
}

public bool CompletedSynchronously
{
get { return ar.CompletedSynchronously; }
}

public bool IsCompleted
{
get { return ar.IsCompleted; }
}

#endregion
}
}

public class FStreamDataEventArgs : EventArgs
{
private byte[] buffer;
private int offset;
private int count;

public FStreamDataEventArgs(byte[] buffer, int offset, int count)
{
if(buffer == null) throw new ArgumentNullException("FStreamDataEventArgs");
if(offset count>buffer.Length) throw new ArgumentOutOfRangeException("FStreamDataEventArgs");

this.buffer = buffer;
this.offset = offset;
this.count = count;
}

/**//// <summary>
/// 数据缓存
/// </summary>
public byte[] Buffer
{
get { return buffer; }
}

/**//// <summary>
/// 数据开始位置
/// </summary>
public int Offset
{
get { return offset; }
}

/**//// <summary>
/// 数据长度
/// </summary>
public int Count
{
get { return count; }
}
}

stream.BeginRead(buffer, 0, byte2read, new AsyncCallback(EndReadCallback), state);

private void EndReadCallback(IAsyncResult asyncResult)
{
object state = asyncResult.AsyncState;
nReadSize = stream.EndRead(asyncResult);
//
}