我如何知道 UdpClient 是否已关闭/处置？

我通过通常的异步回调从 UdpClient 接收数据：

private void OnUdpData(IAsyncResult result)
{
    byte[] data = _udpReceive.EndReceive(result, ref _receiveEndPoint);

    //Snip doing stuff with data

    _udpReceive.BeginReceive(OnUdpData, null);
}

When I Close()主线程中的 UdpClient，回调按我的预期触发，但此时_udpReceive已被处置，我得到了ObjectDisposedException当我尝试打电话时EndReceive()。我期待得到一个空缓冲区。

处理这个问题的正确方法是什么？有没有成员UdpClient我可以在尝试使用它之前进行检查，或者这是将其全部包装在一个中的唯一方法try{}并抓住ObjectDisposedException？对于正常的结束来说，这似乎非常令人讨厌。

您可以执行此操作来检查其是否已处理。当 UdpClient 被释放时，Client 被设置为 null。

private void OnUdpData(IAsyncResult result)
{
    if (_udpReceive.Client == null)
        return;
    byte[] data = _udpReceive.EndReceive(result, ref _receiveEndPoint);

    //Snip doing stuff with data

    if (_udpReceive.Client == null)
        return;
    _udpReceive.BeginReceive(OnUdpData, null);
}

尽管因为您在单独的线程中关闭它，您可能最终会遇到竞争条件。最好只捕获 ObjectDisposeException 和 SocketException。

private void OnUdpData(IAsyncResult result)
{
    try
    {
        byte[] data = _udpReceive.EndReceive(result, ref _receiveEndPoint);

        //Snip doing stuff with data

        _udpReceive.BeginReceive(OnUdpData, null);
    }
    catch (Exception e)
    {
        //You may also get a SocketException if you close it in a separate thread.
        if (e is ObjectDisposedException || e is SocketException)
        {
            //Log it as a trace here
            return;
        }
        //Wasn't an exception we were looking for so rethrow it.
        throw;
    }
}