调用上下文(CallContext)提供了用于存储属性集的数据槽，可以让我们在调用服务器方法时将一些额外数据一并传送过去。当然，这些额外数据有点限制，就是必须要实现 ILogicalThreadAffinative 接口。调用上下文在应用程序域边界被克隆，其数据槽不在其他逻辑线程上的调用上下文之间共享。

我们利用这个特性写一个简单的身份验证例子。

using System;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;
using System.Threading;
using System.Security.Permissions;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters;
using System.Runtime.Serialization.Formatters.Binary;
using System.Runtime.CompilerServices;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;
using System.Runtime.Remoting.Channels.Tcp;
using System.Runtime.Remoting.Messaging;
using System.Runtime.Remoting.Lifetime;
using System.Runtime.Remoting.Services;

namespace Learn.Library.Remoting
{
    public class RemotingTest2
    {
        /// <summary>
        /// 身份验证类型
        /// </summary>
        [Serializable]
        public class Identity : ILogicalThreadAffinative
        {
            private string username;
            private string password;

            public Identity(string username, string password)
            {
                this.username = username;
                this.password = password;
            }

            public string Username
            {
                get { return username; }
                set { username = value; }
            }

            public string Password
            {
                get { return password; }
                set { password = value; }
            }
        }

        /// <summary>
        /// 远程类型
        /// </summary>
        public class Data : MarshalByRefObject
        {
            public void Test()
            {
                // 执行身份验证
                Identity identity = CallContext.GetData("identity") as Identity;
                if (identity != null && identity.Username == "user1" && identity.Password == "pass")
                {
                    Console.WriteLine("Test AppDomain:{0}", AppDomain.CurrentDomain.FriendlyName);
                }
            }
        }

        /// <summary>
        /// 服务器端代码
        /// </summary>
        static void Server()
        {
            AppDomain server = AppDomain.CreateDomain("server");
            server.DoCallBack(delegate
            {
                TcpServerChannel channel = new TcpServerChannel(801);
                ChannelServices.RegisterChannel(channel, false);

                RemotingConfiguration.ApplicationName = "test";
                RemotingConfiguration.RegisterActivatedServiceType(typeof(Data));
            });
        }

        /// <summary>
        /// 客户端代码
        /// </summary>
        static void Client()
        {
            TcpClientChannel channel = new TcpClientChannel();
            ChannelServices.RegisterChannel(channel, false);
            RemotingConfiguration.RegisterActivatedClientType(typeof(Data), "tcp://localhost:801/test");

            // 传送身份验证数据
            CallContext.SetData("identity", new Identity("user1", "pass"));
            Data data = new Data();
            data.Test();
        }

        static void Main()
        {
            Server();
            Client();
        }
    }
}

数据槽中的数据可以双向传输，也就是说我们可以从服务器返回更多的信息给客户端。

using System;
using System.Collections;
using System.Collections.Generic;
using System.Reflection;
using System.Threading;
using System.Security.Permissions;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters;
using System.Runtime.Serialization.Formatters.Binary;
using System.Runtime.CompilerServices;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;
using System.Runtime.Remoting.Channels.Tcp;
using System.Runtime.Remoting.Messaging;
using System.Runtime.Remoting.Lifetime;
using System.Runtime.Remoting.Services;

namespace Learn.Library.Remoting
{
    public class RemotingTest2
    {
        [Serializable]
        public class ServerTime : ILogicalThreadAffinative
        {
            private DateTime time;

            public ServerTime(DateTime time)
            {
                this.time = time;
            }

            public DateTime Time
            {
                get { return time; }
            }
        }

        /// <summary>
        /// 远程类型
        /// </summary>
        public class Data : MarshalByRefObject
        {
            public void Test()
            {
                CallContext.SetData("ExInfo", new ServerTime(DateTime.Now));
                Console.WriteLine("Test AppDomain:{0}", AppDomain.CurrentDomain.FriendlyName);
            }
        }

        /// <summary>
        /// 服务器端代码
        /// </summary>
        static void Server()
        {
            AppDomain server = AppDomain.CreateDomain("server");
            server.DoCallBack(delegate
            {
                TcpServerChannel channel = new TcpServerChannel(801);
                ChannelServices.RegisterChannel(channel, false);

                RemotingConfiguration.ApplicationName = "test";
                RemotingConfiguration.RegisterActivatedServiceType(typeof(Data));
            });
        }

        /// <summary>
        /// 客户端代码
        /// </summary>
        static void Client()
        {
            TcpClientChannel channel = new TcpClientChannel();
            ChannelServices.RegisterChannel(channel, false);
            RemotingConfiguration.RegisterActivatedClientType(typeof(Data), "tcp://localhost:801/test");

            Data data = new Data();
            data.Test();
            Console.WriteLine((CallContext.GetData("ExInfo") as ServerTime).Time);
        }

        static void Main()
        {
            Server();
            Client();
        }
    }
}