设计模式——状态，C# 语言范例

此范例共4个状态，2种操作，没用interface而是用abstract修饰的class实现。

调用：

            TransServer ts = new TransServer();            Console.WriteLine(ts.StopServer());            Console.WriteLine(ts.StartServer());            Console.WriteLine(ts.StartServer());            Console.WriteLine(ts.StopServer());            Console.WriteLine(ts.StopServer());

 

实现：

    internal abstract class State    {        internal TransServer transServer;        public abstract ErrorCode StartServer();        public abstract ErrorCode StopServer();    }    internal class StoppedState : State    {        public StoppedState(TransServer ts)        {            this.transServer = ts;        }        /// <summary>        /// Stopped --> Init --> Worked or Error or Others.        /// </summary>        /// <returns></returns>        public override ErrorCode StartServer()        {            // 下一个状态是initstate            this.transServer.SetState(this.transServer.GetInitState());            // do something...            // finishd...            // 下一个状态是WorkingState            this.transServer.SetState(this.transServer.GetWorkingState());            return ErrorCode.NoError;        }        /// <summary>        /// Do nothing.        /// </summary>        /// <returns></returns>        public override ErrorCode StopServer()        {            // it was already stopped!            return ErrorCode.AlreadyClosed;        }    }    internal class InitState : State    {        public InitState(TransServer ts)        {            this.transServer = ts;        }        /// <summary>        /// Do nothing.        /// </summary>        /// <returns></returns>        public override ErrorCode StartServer()        {            // 正在初始化，不应重复启动。            return ErrorCode.WaitUntilInitialed;        }        /// <summary>        /// Do nothing.        /// </summary>        /// <returns></returns>        public override ErrorCode StopServer()        {            // 初始化可以被终止吗？？            return ErrorCode.WaitUntilInitialed;        }    }    internal class WorkingState : State    {        /// <summary>        ///         /// </summary>        /// <param name="ts"></param>        public WorkingState(TransServer ts)        {            this.transServer = ts;        }        /// <summary>        /// Do nothing.        /// </summary>        /// <returns></returns>        public override ErrorCode StartServer()        {            return ErrorCode.AlreadyStarted;        }        /// <summary>        /// Worked --> Stopped or Error or Others.        /// </summary>        /// <returns></returns>        public override ErrorCode StopServer()        {            // do something...            // finished            this.transServer.SetState(this.transServer.GetStoppedState());            return ErrorCode.NoError;        }    }    internal class ErrorState : State    {        public ErrorState(TransServer ts)        {            this.transServer = ts;        }        public override ErrorCode StartServer()        {            return ErrorCode.UnknowError;        }        public override ErrorCode StopServer()        {            return ErrorCode.UnknowError;        }    }    public class TransServer    {        State stoppedState;        internal State GetStoppedState()        {            return stoppedState;         }        State initState;        internal State GetInitState()        {            return initState;         }        State workingState;        internal State GetWorkingState()        {            return workingState;         }        State errorState;        internal State GetErrorState()        {            return errorState;         }        State state;        /// <summary>        /// 设置当前状态        /// </summary>        internal void SetState(State value)        {            state = value;        }        /// <summary>        /// 默认构造方法        /// </summary>        public TransServer()        {            stoppedState = new StoppedState(this);            initState = new InitState(this);            workingState = new WorkingState(this);            errorState = new ErrorState(this);            state = stoppedState;        }        public ErrorCode StartServer()        {            ErrorCode rv = state.StartServer();            return rv;        }        public ErrorCode StopServer()        {            ErrorCode rv = state.StopServer();            return rv;        }    }

 

    /// <summary>    /// 错误码    /// </summary>    public enum ErrorCode    {        NoError = 0,        AlreadyClosed,        WaitUntilInitialed,        AlreadyStarted,        UnknowError,    }