请问从AppSession继承下来的自定义类为什么无法直接调用SendAsync方法，需要转为IAppSession才能

[ranhuan]

using Google.Protobuf;
using Orleans;
using OrleansBasics;
using SuperSocket;
using SuperSocket.Server;
using System;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;

namespace SocketGate
{
    // 会话对象 要接受返回
    public class ProtobufSession : AppSession, IPlayerObserver
    {
        public IPlayer PlayerGrain { get; internal set; }
        public IGame GameGrain { get; internal set; }

        public void ReceiveMessage(string message)
        {
            Console.WriteLine(message);
        }

        public void ReceiveMessage(Message.OpCode opCode, byte[] data)
        {
            var msg = new byte[4 + data.Length];
            Util.GetBytes((ushort)data.Length).CopyTo(msg, 0);
            Util.GetBytes(opCode).CopyTo(msg, 2);
            data.CopyTo(msg, 4);

            //var rm = new ReadOnlyMemory<byte>(msg);
            Console.WriteLine($"返回消息 {opCode}");
            IAppSession session = (AppSession)this;
            session.SendAsync(msg);
        }
    }
}

[kerryjiang]

There are some concerns regarding package encoding design. For example, some application only allow business logic to send protocol encoded data to remote endpoint. I will review the design soon. Any suggestion would be welcome.