C# ConcurrentDictionary 使用不一致的可访问性？

Question

我正在按照教程构建聊天客户端和服务器，现在我遇到了以下错误:

Inconsistent accessibility: field type 'System.Collections.Concurrent.ConcurrentDictionary<string,ChattingServer.ConnectedClient>' is less accessible than field 'ChattingServer.ChattingService._connectedClients' c:\Users\KOEMXE\Documents\Visual Studio 2012\Projects\ChatApplication\ChattingServer\ChattingService.cs 17  62  ChattingServer

这是相关问题所在的类文件(ChattingService.cs):

using ChattingInterfaces;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;

namespace ChattingServer
{
    [ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple, InstanceContextMode = InstanceContextMode.Single)]
    public class ChattingService : IChattingService
    {
        //private ConnectedClient _connectedClients;

        public ConcurrentDictionary<string, ConnectedClient> _connectedClients = new ConcurrentDictionary<string, ConnectedClient>();

        public int Login(string userName)
        {
            //is anyone else logged in with my name?
            foreach (var client in _connectedClients)
            {
                if(client.Key.ToLower() == userName.ToLower())
                {
                    //if yes
                    return 1;
                }
            }

            var establishedUserConnection = OperationContext.Current.GetCallbackChannel<IClient>();

            ConnectedClient newClient = new ConnectedClient();
            newClient.connection = establishedUserConnection;
            newClient.UserName = userName;



            _connectedClients.TryAdd(userName, newClient);

            return 0;
        }


        public void SendMessageToALL(string message, string userName)
        {
            foreach (var client in _connectedClients)
            {
                if (client.Key.ToLower() != userName.ToLower())
                {
                    client.Value.connection.GetMessage(message, userName);
                }
            }
        }
    }
}

是否需要在其他地方声明 ConcurrentDictionary 对象中的类型？有什么问题？谢谢!

Answer 1

ChattingService 是公共(public)的，它的 _connectedClients 成员也是公共(public)的。但是_connectedClients的类型涉及ChattingServer.ConnectedClient，是不公开的。

假设您要从另一个项目引用您的 ChattingServer 程序集，然后编写如下代码:

using ChattingServer;
...
ConcurrentDictionary<string, ConnectedClient> dict = myChattingService._connectedClients;

ChattingService 类型及其 _connectedClients 字段的可访问性允许您访问该字段，但类型 ConnectedClient 不是公开的，因此，根据您在 ChattingServer 程序集中放置在类型和成员上的可访问性修饰符，您可以访问应隐藏其类型的字段。这就是您收到构建错误的原因:ChattingServer 程序集中类型和成员的可访问性修饰符相互矛盾。

例如，如果您将 ChattingServer.ConnectedClient 设为公开，或将 _connectedClients 设为私有(private)，这将解决问题。