异步服务器到异步客户端的响应在C＃中为NULL

Question

我在客户端和服务器之间进行异步通信。当客户端从服务器（ReceiveCallback）收到响应时，响应将存储在NetworkHandler类的公共静态字符串响应中。我试图在我的GameHandler类中使用此字段，但它表示响应为空。 我确信NetworkHandler中的缓冲区不是空的，因为我检查了它。

我认为这是因为在响应获取值之前调用了NetworkHandler.response，但我不确定并且我不知道如何解决它...

有关详细说明，请参阅代码中的注释...

请查看此图片以查看GameHandler中的空值：http://i.imgur.com/BPVDlhf.png并在此处查看NetworkHandler中的正确值：http://i.imgur.com/vfY2IuD.png

class NetworkHandler
{
    public static string response = String.Empty;

    private static void ReceiveCallback(IAsyncResult AR)
    {         
        Socket remote = (Socket)AR.AsyncState;
        int received = remote.EndReceive(AR);

        byte[] dataBuffer = new byte[received];            
        Array.Copy(_buffer, dataBuffer, received);
        string serverData = Encoding.ASCII.GetString(dataBuffer);
        response = serverData;
    }

    private static void SendCallback(IAsyncResult AR)
    {
        Socket remote = (Socket)AR.AsyncState;
        int sent = remote.EndSend(AR);
        remote.BeginReceive(_buffer, 0, _size, SocketFlags.None, new AsyncCallback(ReceiveCallback), remote);
    }

    public static void sendData(string data)
    {
        byte[] message = Encoding.ASCII.GetBytes(data);
        _client.BeginSend(message, 0, message.Length, SocketFlags.None, new AsyncCallback(SendCallback), _client);
    }

    private static void ConnectCallback(IAsyncResult AR)
    {
        _client = (Socket)AR.AsyncState;
        try
        {
            _client.EndConnect(AR);
            _client.BeginReceive(_buffer, 0, _size, SocketFlags.None, new AsyncCallback(ReceiveCallback), _client);
        }
        catch (SocketException e)
        {
            Console.WriteLine(e.ToString());
        }
    }
}

class GameHandler
{
    public void StartGame()
    {
        // SEND DATA USING BEGINSEND()
        SendData("<sg>");

        // THIS VALUE IS NULL!!! :(
        _response = NetworkHandler.response;

        // SO CODE INSIDE IF IS NOT EXECUTED :(
        if (_response != null)
        {
            // If you are the drawer.
            if (_response.Substring(0, 5) == "<dra>")
            etc.........
         }
     }

     public void SendData(string data)
     {
        NetworkHandler.sendData(data);
     }
}