如何在调用WCF服务之前弹出一个确认对话框？

其实这个问题可以通过WCF的扩展来完成，具体来说这个扩展涉及到一个我们不太常用的组件“InteractiveChannelInitializer”，在我的《WCF全面解析》中对它有过概括性的介绍。InteractiveChannelInitializer实现了接口IInteractiveChannelInitializer，从名称可以看出这是一个“交互性”的“信道初始化器”，在一般情况下我们用它来动态地指定客户端调用凭证（比如在弹出的登录对话框中输入用户名和密码）。而上面这个问题就可以通过自定义InteractiveChannelInitializer来实现，我为此写了一个简单的实例（源代码从这里下载）。
右图所示的是实例的运行界面。我们以Windows Form应用的方式编写了一个“计算器”，计算结果通过调用WCF服务来获取。在每次调用服务之前都会弹出一个确认对话框，真正的服务调用只有在用户确认之后方能进行。
用于实现“服务调用确认”的自定义InteractiveChannelInitializer（InvocationConfirmationInteractiveChannelInitializer）定义如下。我们在BeginDisplayInitializationUI方法中弹出一个确认对话框，并将用户的确认选择封装到一个简单的AsyncResult对象中返回。在EndDisplayInitializationUI方法中，通过AsyncResult对象确认用户是否取消本次服务调用，如果是则抛出一个自定义的InvocationCancelException异常。

   1: public class InvocationConfirmationInteractiveChannelInitializer : IInteractiveChannelInitializer

   2: {

   3:     public const string ConfirmMessage = "程序执行过程涉及到WCF服务调用，是否继续？";

   4:     public IAsyncResult BeginDisplayInitializationUI(IClientChannel channel, AsyncCallback callback, object state)

   5:     {

   6:         bool cancel = MessageBox.Show(ConfirmMessage, "WCF服务调用确认", MessageBoxButtons.YesNo) == DialogResult.No;

   7:         return new SimpleAsynsResult(cancel);

   8:     }

   9:  

  10:     public void EndDisplayInitializationUI(IAsyncResult result)
其实这个问题可以通过WCF的扩展来完成，具体来说这个扩展涉及到一个我们不太常用的组件“InteractiveChannelInitializer”，在我的《WCF全面解析》中对它有过概括性的介绍。InteractiveChannelInitializer实现了接口IInteractiveChannelInitializer，从名称可以看出这是一个“交互性”的“信道初始化器”，在一般情况下我们用它来动态地指定客户端调用凭证（比如在弹出的登录对话框中输入用户名和密码）。而上面这个问题就可以通过自定义InteractiveChannelInitializer来实现，我为此写了一个简单的实例（源代码从这里下载）。
  
右图所示的是实例的运行界面。我们以Windows Form应用的方式编写了一个“计算器”，计算结果通过调用WCF服务来获取。在每次调用服务之前都会弹出一个确认对话框，真正的服务调用只有在用户确认之后方能进行。
  
用于实现“服务调用确认”的自定义InteractiveChannelInitializer（InvocationConfirmationInteractiveChannelInitializer）定义如下。我们在BeginDisplayInitializationUI方法中弹出一个确认对话框，并将用户的确认选择封装到一个简单的AsyncResult对象中返回。在EndDisplayInitializationUI方法中，通过AsyncResult对象确认用户是否取消本次服务调用，如果是则抛出一个自定义的InvocationCancelException异常。
  
   
     
   1: public class InvocationConfirmationInteractiveChannelInitializer : IInteractiveChannelInitializer
    
   2: {
    
   3:     public const string ConfirmMessage = "程序执行过程涉及到WCF服务调用，是否继续？";
    
   4:     public IAsyncResult BeginDisplayInitializationUI(IClientChannel channel, AsyncCallback callback, object state)
    
   5:     {
    
   6:         bool cancel = MessageBox.Show(ConfirmMessage, "WCF服务调用确认", MessageBoxButtons.YesNo) == DialogResult.No;
    
   7:         return new SimpleAsynsResult(cancel);
    
   8:     }
    
   9:  
    
  10:     public void EndDisplayInitializationUI(IAsyncResult result)
    
  11:     {
    
  12:         SimpleAsynsResult asyncResult = (SimpleAsynsResult)result;
    
  13:         if((bool)asyncResult.AsyncState)
    
  14:         {
    
  15:             throw new InvocationCancelException("WCF服务调用被取消");
    
  16:         }
    
  17:     }
    
  18: }
    
  19:  
    
  20: public class SimpleAsynsResult:IAsyncResult
    
  21: {
    
  22:     public SimpleAsynsResult(object state)
    
  23:     {
    
  24:         this.AsyncState = state;
    
  25:     }
    
  26:  
    
  27:     public object AsyncState { get; private set; }
    
  28:     public WaitHandle AsyncWaitHandle { get; private set; }
    
  29:     public bool CompletedSynchronously
    
  30:     {
    
  31:         get { return true; }
    
  32:     }
    
  33:     public bool IsCompleted
    
  34:     {
    
  35:         get { return true; }
    
  36:     }
    
  37: }
我们通过一个自定义的ContractBehavior（InvocationConfirmationBehaviorAttribute ）将上面自定义的InvocationConfirmationInteractiveChannelInitializer应用到客户端运行时。如下面的代码片断所示，在实现的ApplyClientBehavior方法中，我们创建了一个InvocationConfirmationInteractiveChannelInitializer对象并将其添加到客户端运行时的InteractiveChannelInitializers集合中。
  
    
   1: [AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface)]
    
   2: public class InvocationConfirmationBehaviorAttribute : Attribute, IContractBehavior
    
   3: {
    
   4:     public void AddBindingParameters(ContractDescription contractDescription, ServiceEndpoint endpoint, BindingParameterCollection bindingParameters) { }
    
   5:     public void ApplyClientBehavior(ContractDescription contractDescription, ServiceEndpoint endpoint, ClientRuntime clientRuntime)
    
   6:     {
    
   7:         clientRuntime.InteractiveChannelInitializers.Add(new InvocationConfirmationInteractiveChannelInitializer());
    
   8:     }
    
   9:     public void ApplyDispatchBehavior(ContractDescription contractDescription, ServiceEndpoint endpoint, DispatchRuntime dispatchRuntime) { }
    
  10:     public void Validate(ContractDescription contractDescription, ServiceEndpoint endpoint) { }
    
  11: }
以特性形式定义的InvocationConfirmationBehaviorAttribute直接以如下的方式直接应用到作为服务契约的ICalcualtor接口中：
  
    
   1: [ServiceContract(Name = "CalculatorService", Namespace ="http://www.artech.com/")]
    
   2: [InvocationConfirmationBehavior]
    
   3: public interface ICalculator
    
   4: {
    
   5:     [OperationContract]
    
   6:     double Add(double x, double y);
    
   7: }
那么在进行服务调用的时候，确认对话框会自动弹出来。如果用户选择终止当前服务调用，那么InvocationCancelException异常会被抛出来，我们只需要捕捉该类型的异常即可。如下所示的是“=”按钮的Click事件代码：
      
   1: public partial class Form1 : Form
    
   2: {
    
   3:     //其他成员
    
   4:     private void buttonCalculate_Click(object sender, EventArgs e)
    
   5:     {
    
   6:         this.textBoxResult.Text = string.Empty;
    
   7:         using (ChannelFactory<ICalculator> channelfactory = new ChannelFactory<ICalculator>("calculatorservice"))
    
   8:         {
    
   9:             ICalculator calculator = channelfactory.CreateChannel();
    
  10:             try
    
  11:             {
    
  12:                 double op1 = double.Parse(this.textBoxOp1.Text);
    
  13:                 double op2 = double.Parse(this.textBoxOp2.Text);
    
  14:                 double result = calculator.Add(op1,op2);
    
  15:                 this.textBoxResult.Text = result.ToString();
    
  16:             }
    
  17:             catch (InvocationCancelException)
    
  18:             {
    
  19:             }
    
  20:             catch (Exception ex)
    
  21:             {
    
  22:                 MessageBox.Show(ex.Message);
    
  23:             }
    
  24:         }
    
  25:     }
    
  26: }

  11:     {

  12:         SimpleAsynsResult asyncResult = (SimpleAsynsResult)result;

  13:         if((bool)asyncResult.AsyncState)

  14:         {

  15:             throw new InvocationCancelException("WCF服务调用被取消");

  16:         }

  17:     }

  18: }

  19:  

  20: public class SimpleAsynsResult:IAsyncResult

  21: {

  22:     public SimpleAsynsResult(object state)

  23:     {

  24:         this.AsyncState = state;

  25:     }

  26:  

  27:     public object AsyncState { get; private set; }

  28:     public WaitHandle AsyncWaitHandle { get; private set; }

  29:     public bool CompletedSynchronously

  30:     {

  31:         get { return true; }

  32:     }

  33:     public bool IsCompleted

  34:     {

  35:         get { return true; }

  36:     }

  37: }

我们通过一个自定义的ContractBehavior（InvocationConfirmationBehaviorAttribute ）将上面自定义的InvocationConfirmationInteractiveChannelInitializer应用到客户端运行时。如下面的代码片断所示，在实现的ApplyClientBehavior方法中，我们创建了一个InvocationConfirmationInteractiveChannelInitializer对象并将其添加到客户端运行时的InteractiveChannelInitializers集合中。

   1: [AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface)]

   2: public class InvocationConfirmationBehaviorAttribute : Attribute, IContractBehavior

   3: {

   4:     public void AddBindingParameters(ContractDescription contractDescription, ServiceEndpoint endpoint, BindingParameterCollection bindingParameters) { }

   5:     public void ApplyClientBehavior(ContractDescription contractDescription, ServiceEndpoint endpoint, ClientRuntime clientRuntime)

   6:     {

   7:         clientRuntime.InteractiveChannelInitializers.Add(new InvocationConfirmationInteractiveChannelInitializer());

   8:     }

   9:     public void ApplyDispatchBehavior(ContractDescription contractDescription, ServiceEndpoint endpoint, DispatchRuntime dispatchRuntime) { }

  10:     public void Validate(ContractDescription contractDescription, ServiceEndpoint endpoint) { }

  11: }

以特性形式定义的InvocationConfirmationBehaviorAttribute直接以如下的方式直接应用到作为服务契约的ICalcualtor接口中：

   1: [ServiceContract(Name = "CalculatorService", Namespace ="http://www.artech.com/")]

   2: [InvocationConfirmationBehavior]

   3: public interface ICalculator

   4: {

   5:     [OperationContract]

   6:     double Add(double x, double y);

   7: }

那么在进行服务调用的时候，确认对话框会自动弹出来。如果用户选择终止当前服务调用，那么InvocationCancelException异常会被抛出来，我们只需要捕捉该类型的异常即可。如下所示的是“=”按钮的Click事件代码：

   1: public partial class Form1 : Form

   2: {

   3:     //其他成员

   4:     private void buttonCalculate_Click(object sender, EventArgs e)

   5:     {

   6:         this.textBoxResult.Text = string.Empty;

   7:         using (ChannelFactory<ICalculator> channelfactory = new ChannelFactory<ICalculator>("calculatorservice"))

   8:         {

   9:             ICalculator calculator = channelfactory.CreateChannel();

  10:             try

  11:             {

  12:                 double op1 = double.Parse(this.textBoxOp1.Text);

  13:                 double op2 = double.Parse(this.textBoxOp2.Text);

  14:                 double result = calculator.Add(op1,op2);

  15:                 this.textBoxResult.Text = result.ToString();

  16:             }

  17:             catch (InvocationCancelException)

  18:             {

  19:             }

  20:             catch (Exception ex)

  21:             {

  22:                 MessageBox.Show(ex.Message);

  23:             }

  24:         }

  25:     }

  26: }   备注：本文并非本人撰写的，原文是出自： http://www.cnblogs.com/artech/archive/2012/10/07/2713574.html