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HOW TO：建立雙工合約

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本主題說明的基本步驟可用來建立使用雙工 (雙向) 合約的方法。雙工合約可供用戶端與伺服器彼此各自進行通訊，方便任何一方初始化對另一方的呼叫。雙工合約是 Windows Communication Foundation (WCF) 服務可用的三種訊息模式之一。其他兩種訊息模式分別是單向和要求-回覆。雙工合約是由用戶端和伺服器之間的兩個單向合約組成，而且不需要相互關聯方法呼叫。當您的服務必須查詢用戶端以獲得更多資訊，或是明確地在用戶端上引發事件時，請使用這種合約。如需詳細資訊建立雙工合約之用戶端應用程式的詳細資訊，請參閱 HOW TO：使用雙工合約存取服務。如需實用範例，請參閱雙工。

若要建立雙工合約

  1. 建立可組成雙工合約伺服器端的介面。

  2. 將 ServiceContractAttribute 類別套用到介面。

    <ServiceContract(Namespace:="http://Microsoft.ServiceModel.Samples", SessionMode:=SessionMode.Required, _
                CallbackContract:=GetType(ICalculatorDuplexCallback))> _
Public Interface ICalculatorDuplex

    <OperationContract(IsOneWay:=True)> _
    Sub Clear()
    <OperationContract(IsOneWay:=True)> _
    Sub AddTo(ByVal n As Double)
    <OperationContract(IsOneWay:=True)> _
    Sub SubtractFrom(ByVal n As Double)
    <OperationContract(IsOneWay:=True)> _
    Sub MultiplyBy(ByVal n As Double)
    <OperationContract(IsOneWay:=True)> _
    Sub DivideBy(ByVal n As Double)
End Interface

    [ServiceContract(Namespace = "http://Microsoft.ServiceModel.Samples", SessionMode=SessionMode.Required,
                 CallbackContract=typeof(ICalculatorDuplexCallback))]
public interface ICalculatorDuplex
{
    [OperationContract(IsOneWay=true)]
    void Clear();
    [OperationContract(IsOneWay = true)]
    void AddTo(double n);
    [OperationContract(IsOneWay = true)]
    void SubtractFrom(double n);
    [OperationContract(IsOneWay = true)]
    void MultiplyBy(double n);
    [OperationContract(IsOneWay = true)]
    void DivideBy(double n);
}

  3. 在介面中宣告方法簽章。

  4. 將 OperationContractAttribute 類別套用到每個必須是公用合約一部分的方法簽章上。

  5. 建立可定義作業集合 (供服務在用戶端上加以叫用) 的回呼介面。

    Public Interface ICalculatorDuplexCallback
    <OperationContract(IsOneWay:=True)> _
    Sub Equals(ByVal result As Double)
    <OperationContract(IsOneWay:=True)> _
    Sub Equation(ByVal eqn As String)
end interface 

    public interface ICalculatorDuplexCallback
{
    [OperationContract(IsOneWay = true)]
    void Equals(double result);
    [OperationContract(IsOneWay = true)]
    void Equation(string eqn);
}

  6. 在回呼介面中宣告方法簽章。

  7. 將 OperationContractAttribute 類別套用到每個必須是公用合約一部分的方法簽章上。

  8. 將主要介面中的 CallbackContract 屬性設為回呼介面的型別，以將兩個介面連接至雙工合約。

若要在用戶端上呼叫方法

  1. 在服務的主要合約實作中，宣告回呼介面的變數。

  2. 將變數設為由 OperationContext 類別之 GetCallbackChannel 方法傳回的物件參考。

    Dim callback As ICalculatorDuplexCallback

    ICalculatorDuplexCallback callback = null;

    callback = OperationContext.Current.GetCallbackChannel(Of ICalculatorDuplexCallback)()

    callback = OperationContext.Current.GetCallbackChannel<ICalculatorDuplexCallback>();

  3. 呼叫回呼介面定義的方法。

範例

下列程式碼範例會示範雙工通訊。服務合約包含可往前與往後的服務作業。用戶端合約包含可報告自身位置的服務作業。

' Define a duplex service contract.
' A duplex contract consists of two interfaces.
' The primary interface is used to send messages from client to service.
' The callback interface is used to send messages from service back to client.
' ICalculatorDuplex allows one to perform multiple operations on a running result.
' The result is sent back after each operation on the ICalculatorCallback interface.
<ServiceContract(Namespace:="http://Microsoft.ServiceModel.Samples", SessionMode:=SessionMode.Required, _
                CallbackContract:=GetType(ICalculatorDuplexCallback))> _
Public Interface ICalculatorDuplex

    <OperationContract(IsOneWay:=True)> _
    Sub Clear()
    <OperationContract(IsOneWay:=True)> _
    Sub AddTo(ByVal n As Double)
    <OperationContract(IsOneWay:=True)> _
    Sub SubtractFrom(ByVal n As Double)
    <OperationContract(IsOneWay:=True)> _
    Sub MultiplyBy(ByVal n As Double)
    <OperationContract(IsOneWay:=True)> _
    Sub DivideBy(ByVal n As Double)
End Interface

' The callback interface is used to send messages from service back to client.
' The Equals operation will return the current result after each operation.
' The Equation opertion will return the complete equation after Clear() is called.
Public Interface ICalculatorDuplexCallback
    <OperationContract(IsOneWay:=True)> _
    Sub Equals(ByVal result As Double)
    <OperationContract(IsOneWay:=True)> _
    Sub Equation(ByVal eqn As String)
end interface 

' Service class which implements a duplex service contract.
' Use an InstanceContextMode of PerSession to store the result
' An instance of the service will be bound to each duplex session
<ServiceBehavior(InstanceContextMode:=InstanceContextMode.PerSession)> _
Public Class CalculatorService
    Implements ICalculatorDuplex
    Dim result As Double
    Dim equation As String
    Dim callback As ICalculatorDuplexCallback

    Public Sub New()
        result = 0D
        equation = result.ToString()
        callback = OperationContext.Current.GetCallbackChannel(Of ICalculatorDuplexCallback)()

    End Sub
    Public Sub AddTo(ByVal n As Double) Implements ICalculatorDuplex.AddTo
        result += n
        equation += " + " + n.ToString()
        callback.Equals(result)
    End Sub

    Public Sub Clear() Implements ICalculatorDuplex.Clear
        callback.Equation(equation + " = " + result.ToString())
        result = 0D
        equation = result.ToString()
    End Sub

    Public Sub DivideBy(ByVal n As Double) Implements ICalculatorDuplex.DivideBy
        result /= n
        equation += " / " + n.ToString()
        callback.Equals(result)
    End Sub

    Public Sub MultiplyBy(ByVal n As Double) Implements ICalculatorDuplex.MultiplyBy
        result *= n
        equation += " * " + n.ToString()
        callback.Equals(result)
    End Sub

    Public Sub SubtractFrom(ByVal n As Double) Implements ICalculatorDuplex.SubtractFrom
        result -= n
        equation += " - " + n.ToString()
        callback.Equals(result)
    End Sub
End Class

// Define a duplex service contract.
// A duplex contract consists of two interfaces.
// The primary interface is used to send messages from client to service.
// The callback interface is used to send messages from service back to client.
// ICalculatorDuplex allows one to perform multiple operations on a running result.
// The result is sent back after each operation on the ICalculatorCallback interface.
[ServiceContract(Namespace = "http://Microsoft.ServiceModel.Samples", SessionMode=SessionMode.Required,
                 CallbackContract=typeof(ICalculatorDuplexCallback))]
public interface ICalculatorDuplex
{
    [OperationContract(IsOneWay=true)]
    void Clear();
    [OperationContract(IsOneWay = true)]
    void AddTo(double n);
    [OperationContract(IsOneWay = true)]
    void SubtractFrom(double n);
    [OperationContract(IsOneWay = true)]
    void MultiplyBy(double n);
    [OperationContract(IsOneWay = true)]
    void DivideBy(double n);
}
// The callback interface is used to send messages from service back to client.
// The Equals operation will return the current result after each operation.
// The Equation opertion will return the complete equation after Clear() is called.
public interface ICalculatorDuplexCallback
{
    [OperationContract(IsOneWay = true)]
    void Equals(double result);
    [OperationContract(IsOneWay = true)]
    void Equation(string eqn);
}
// Service class which implements a duplex service contract.
// Use an InstanceContextMode of PerSession to store the result
// An instance of the service will be bound to each duplex session
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerSession)]
public class CalculatorService : ICalculatorDuplex
{
    double result;
    string equation;
    ICalculatorDuplexCallback callback = null;

    public CalculatorService()
    {
        result = 0.0D;
        equation = result.ToString();
        callback = OperationContext.Current.GetCallbackChannel<ICalculatorDuplexCallback>();
    }

    public void Clear()
    {
        callback.Equation(equation + " = " + result.ToString());
        result = 0.0D;
        equation = result.ToString();
    }

    public void AddTo(double n)
    {
        result += n;
        equation += " + " + n.ToString();
        callback.Equals(result);
    }

    public void SubtractFrom(double n)
    {
        result -= n;
        equation += " - " + n.ToString();
        callback.Equals(result);
    }

    public void MultiplyBy(double n)
    {
        result *= n;
        equation += " * " + n.ToString();
        callback.Equals(result);
    }

    public void DivideBy(double n)
    {
        result /= n;
        equation += " / " + n.ToString();
        callback.Equals(result);
    }

}

  • 套用 ServiceContractAttribute 和 OperationContractAttribute 屬性可自動產生 Web 服務描述語言 (WSDL) 格式的服務合約定義。

  • 使用 ServiceModel 中繼資料公用程式工具 (Svcutil.exe) 來擷取用戶端的 WSDL 文件與 (選擇性) 程式碼及組態。

  • 您必須保護公開雙工服務的端點安全。當服務收到雙工訊息時，會查看該傳入訊息中的 ReplyTo 項目，以判斷傳送回覆的位置。如果通道不安全，那麼未受信任的用戶端可能會傳送惡意訊息，其中包含目標電腦的 ReplyTo，而導致該目標電腦發生阻絕服務。如果是一般的要求-回覆訊息，這根本不是問題，因為電腦會忽略 ReplyTo 並且在原始傳入訊息所用的通道上傳送回應。

另請參閱

工作

HOW TO：使用雙工合約存取服務
雙工
HOW TO：定義 Windows Communication Foundation 服務合約
工作階段

參考

ServiceContractAttribute
OperationContractAttribute

概念

設計與實作服務