TcpClient and NetworkStream dispose problem.

Question

I'm using this piece of code to process a connection to a server and read data from the client

using(var client = _listener.EndAcceptTcpClient(ar))
{
        var clientStream = client.GetStream();
        // Get the request message 
        Messages.ReceiveMessage(clientStream, msg => ProcessRequest(msg, clientStream));
}

Now, the ReceiveMessage method calls BeginRead() on the Stream passed as a parameter, but I'm getting an ObjectDisposedException.

I know that a solution is to call stream.Dispose() when I don't need the Stream anymore, but I'm really looking for a solution where I can maintain the use of the using clause.

Thanks

Answer 1

You can do this:

using (var client = _listener.EndAcceptTcpClient(ar))
{
    var clientStream = client.GetStream();

    using (var eh = new ManualResetEvent(false))
    {
        // Get the request message 
        Messages.ReceiveMessage(clientStream, msg =>
            {
                ProcessRequest(msg, clientStream);
                eh.Set();
            });

        eh.WaitOne();
    }
}

One caveat: if there's anywhere sensible (a class instance) to store the ManualResetEvent, so that it can be reused, do so -- since creating/destroying lots of these can be a bit piggy.

Also note that I'm assuming from the behavior you describe in your post that ReceiveMessage() is an asynchronous operation.

Answer 2

There are two possibilities here.

First, you could take this asynchronous process and block until it completes, allowing you to preserve the using statement. This is the approach suggested by Ben M here.

Alternatively, you can remove the using statement, and dispose of the client variable yourself. This may seem more cumbersome than using the compiler's syntax for using, but it does provide the advantage of allowing you to maintain the asynchronous behavior your currently are trying to take advantage of in this situation, and eliminates the need for blocks. However, this will require you to store the variable, and dispose of it yourself in an appropriate place (possibly at the end of your delegate, but that also probably requires checking it later, just in case the delegate is never called).

The "using" statement in C# is great, but there are situations where it is not appropriate, and this may be one of them (if you need to preserve the asyncrhonous behavior).