public override IAsyncResult BeginRead(byte[] buffer, int offset, int count, AsyncCallback callback, object state)
{
if (buffer is null)
{
throw new ArgumentNullException(nameof(buffer));
}
void wrappedCallback(IAsyncResult result)
{
lastRead = SourceStream.EndRead(result);
outStream.Write(buffer, offset, lastRead);
callback?.Invoke(result);
}
return(SourceStream.BeginRead(buffer, offset, count, wrappedCallback, state));
}