c# - 在这种情况下，避免ObjectDisposedException的正确方法是？

Question

我当前在下一行上收到一个ObjectDisposedException。

var client = ((Socket) asyncResult.AsyncState).EndAccept(asyncResult);

System.ObjectDisposedException: 'Cannot access a disposed object. Object name: 'System.Net.Sockets.Socket'.'

我只是想知道，避免这种错误的正确方法(按照最佳实践)是什么？我不确定如何处理它，如何检查它是否已预先处置，但是我应该做什么？或检查其他内容。

我是自学C#，所以我从没学过类似的东西，有人可以提供一些见解吗？

这是完整的类(class):

internal sealed class SocketHandler : IDisposable
{
    private static readonly ILogger Logger = LogManager.GetCurrentClassLogger();

    private readonly Socket _serverSocket;

    public SocketHandler()
    {
        _serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

        Load();
    }

    public void Dispose()
    {
        _serverSocket?.Close(); // close also calls dispose...
    }

    private void Load()
    {
        var config = Program.Server.ConfigHandler;

        _serverSocket.Bind(new IPEndPoint(IPAddress.Any, config.GetConfigValueByKey("network.sockets.port").ToInt()));
        _serverSocket.Listen(int.Parse(config.GetConfigValueByKey("network.sockets.backlog")));
        _serverSocket.BeginAccept(OnAcceptConnection, _serverSocket);
    }

    private void OnAcceptConnection(IAsyncResult asyncResult)
    {
        try
        {
            if (_serverSocket == null)
            {
                return;
            }

            var client = ((Socket) asyncResult.AsyncState).EndAccept(asyncResult);

            var playerHandler = Program.Server.BaseHandler.PlayerHandler;
            var players = playerHandler.Players;

            var config = Program.Server.ConfigHandler;

            var maxConnections = int.Parse(config.GetConfigValueByKey("game.players.limit"));
            var maxConnectionsPerIp = int.Parse(config.GetConfigValueByKey("game.players.ip_limit"));

            if (players.Count >= maxConnections)
            {
                Logger.Warn("Incoming connection was refused because the player limit was exceeded.");

                client.Shutdown(SocketShutdown.Both);
                client.Close();

                return;
            }

            if (players.Values.Count(x => x != null && !x._disconnected && x.getIp() == client.RemoteEndPoint.ToString().Split(':')[0]) > maxConnectionsPerIp)
            {
                Logger.Warn("Incoming connection was refused because the IP limit was exceeded.");

                client.Shutdown(SocketShutdown.Both);
                client.Close();

                return;
            }

            var clientId = Randomizer.Next(1, 10000);

            Program.Server.BaseHandler.PlayerHandler.TryAddPlayer(clientId, new Player(clientId, client, new InitialPacketParser()));
        }
        catch (SocketException socketException)
        {
            Logger.Fatal(socketException, "Failed to accept socket connection.");
        }
        finally
        {
            _serverSocket?.BeginAccept(OnAcceptConnection, _serverSocket);
        }
    }
}

Answer 1

据我了解reference source，Socket本身不是Dispose。因此，由于您的_serverSocket是private，因此您是唯一可以控制其处置时间的人。

您的OnAcceptConnection()方法已经开始尝试进行检查，但还不是完全。

在Dispose()方法(或Close()或Dispose() _serverSocket的任何其他位置)中，您还需要将_serverSocket设置为null。您可以通过线程安全的方式执行以下操作:

public class SocketHandler
{
    private Socket _serverSocket; // not read-only

    /* ... */

    public void Dispose()
    {
        Socket tmp = _serverSocket; // save instance
        _serverSocket = null; // set field to null
        tmp?.Close();
    }

现在，您的 OnAcceptConnection()在检查 if (_serverSocket == null)时返回，因此可以避免该异常。