WCF 中状态的保存

WCF 状态的保存分为两步:
      (1) 使用SessionMode 来使Session有效化
            

            [ServiceContract(SessionMode=SessionMode.Required)]
            public interface ICalculator
            {
                    [OperationContract(IsOneWay=true)]
                    void Adds(double x);

                    [OperationContract]
                    double GetResult();
            }

      (2)ServiceBehavior 里面利用参数InstanceContextMode设定到底使用哪一种Session方式
            

            [ServiceBehavior(InstanceContextMode=InstanceContextMode.PerCall)]
            public class CalculatorService:ICalculator
          {
              private double _result;

              public double Result
              {
                  get { return _result; }
                  set { _result = value; }
              }

              public void Adds(double x)
              {
                  Console.WriteLine("The Add Method is invoked and The current SessionID is {0} ",OperationContext.Current.SessionId);
                  this._result += x;
              }

              public double GetResult()
              {
                  Console.WriteLine("The GetResult Method is invoked and The current SessionID is {0} ", OperationContext.Current.SessionId);
                  return this._result;
              }

              public CalculatorService()
              {
                  Console.WriteLine("CalculatorService object has been Created ");
              }

              ~CalculatorService()
              {
                  Console.WriteLine("CalculatorService object has been destoried ");
              }

          }

SessionMode 有三种值：
(1)Allowed 默认选值，允许但不强制使用Session
(2)Required 强制使用Session
(3)NotAllowed 不允许使用Session 

InstanceContextMode 有三种值:
(1) Percall 为user的每一次调用生成一个SessionID
      生命周期:调用开始 ---->调用结束，这种情况和不使用Session是一样的
(2) PerSession 为每个用户生成一个SessionID
      生命周期:客户端代理生成--->客户端代理关闭   和最原先的Session是一样的
(3) Seigle 生成唯一的SessionID，所有的用户共享 从host创建---->host 关闭，和Application 一样