对客户端的 WCF 服务调用

Question

我正在尝试创建 WCF 服务来处理客户端请求和修改数据库。除了我的用户客户端，我还有其他接口，可以调用我的 WCF 服务并修改数据库。

我的问题是，我想通知我的客户由于我的其他接口而发生的数据库更改。

所以基本上：客户端是运行，由 WAS/IIS 托管的 WCF 服务，数据库更改和服务应将更改通知我所有连接的客户端。

我的用户客户端是简单的 WinForms 应用程序，服务引用了它们。

我想避免从客户端发起调用并等待响应，我更希望服务向客户端方向进行调用。

我的问题是有没有办法实现这个，或者我应该使用类似监听器的东西？

Answer 1

这可以在WCF中实现。

实施所谓的 'duplex communication pattern'，这基本上是两个单向合同。

Here is an MSDN article for just that... How to: Create a Duplex Contract

"This topic shows the basic steps to create methods that use a duplex (two-way) contract. A duplex contract allows clients and servers to communicate with each other independently so that either can initiate calls to the other. The duplex contract is one of three message patterns available to Windows Communication Foundation (WCF) services. The other two message patterns are one-way and request-reply. A duplex contract consists of two one-way contracts between the client and the server and does not require that the method calls be correlated. Use this kind of contract when your service must query the client for more information or explicitly raise events on the client."

Encase 他们删除了页面，我不太喜欢 link 只回答...

// 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);
    }
}

对客户端的 WCF 服务调用

WCF service calls to clients

.net

c#

service

wcf

client